Как в WordPress изменить шрифт заголовка выводимой статьи?

Привет!У меня есть сайт на WordPress.Мне нужно изменить шрифт заголовка статьи.

Index.php

<?php get_header(); ?>
<div class="banner">
  <div class="banner-image">
      <?php if( get_field('des-off', 'options') == 'true' ):  
$image = get_field('desc-img', 'options');
if( !empty($image) ): 
$size = 'desctop';
    $thumb = $image['sizes'][ $size ];
    ?>
    <img class="dont-show hidden-xs" src="<?php echo $thumb; ?>" />
   <?php endif; endif; ?>

<?php if( get_field('mob-off', 'options') == 'true' ):  
$image = get_field('mob-img', 'options');
if( !empty($image) ): 
$size = 'mobail';
    $thumb = $image['sizes'][ $size ];
    ?>
    <img class="mobi-logo hidden-sm hidden-md hidden-lg" src="<?php echo $thumb; ?>" />
    <?php endif; endif; ?>
     <?php if( get_field('des-off', 'options') == 'true' ):  ?>  
    <div class="banner-title dont-show hidden-xs">
      <div class="banner-tbl dont-show">
        <div class="banner-td dont-show">
          <div class="container dont-show">
             <?php the_field('des-ban', 'options'); ?>
          </div>
        </div>
      </div>
    </div>
    <?php endif; ?>
  <?php if( get_field('mob-off', 'options') == 'true' ):  ?>  
    <!--mobil banner-->
    <div class="banner-title dont-show hidden-sm hidden-md hidden-lg">
      <div class="banner-tbl dont-show">
        <div class="banner-td dont-show">
          <div class="container dont-show mob-ban">
             <?php the_field('mob-ban', 'options'); ?>
          </div>
        </div>
      </div>
    </div>
      <?php endif; ?>
  </div>
    <!--Форма подписки после баннера-->
  <?php if( get_field('home-pdf2', 'options') == 'true' ): ?>  
  <div class="container dont-show">
    <div class="row product">
        <div class="col-xs-6 col-sm-3 col-md-3 cover">
            <img alt="<?php bloginfo('name'); ?>" src="<?php bloginfo('template_url'); ?>/images/book-cover-top.png" />
        </div>
        <div class="col-xs-12 col-sm-12 col-md-9 subscribe">
            <div style="font-family: 'PT Serif';">
            <?php the_field('home-pdf1', 'options'); ?>
                <div>
            <form class="form-inline">
                <div class="form-group">
                    <input type="name" class="form-control input-lg" id="InputName" placeholder="<?php printf( _e( 'Your Name', 'zaxidna' )); ?>">
                </div>
                <div class="form-group">
                    <input type="email" class="form-control input-lg" id="InputEmail" placeholder="<?php printf( _e( 'E-mail', 'zaxidna' )); ?>">
                </div>
                <button type="submit" class="btn btn-lg"><?php printf( _e( 'Get Now', 'zaxidna' )); ?></button>
            </form>
        </div>
    </div>
</div>
    <?php endif; ?>
<!--  END   Форма подписки после баннера-->
</div>
<div class="container mobi-bg">
  <div class="row">
    <div class="col-xs-12 col-md-8">
      <nav class="categories hidden-xs">
        <?php wp_nav_menu(array('menu' => 'categories', 'menu_class' => 'list-inline')); ?>
        <hr />
      </nav>
      <main id="book-form" class="content">
        <?php if ( have_posts() ) : ?>
            <?php
            while ( have_posts() ) : the_post();?>
                <?php get_template_part( 'content', get_post_format() );
            endwhile;
?>
<nav>
<?php wpex_pagination(); ?>
</nav>
<?php
        else :
            get_template_part( 'content', 'none' );
        endif;
        ?>
      </main>
    </div>
    <div class="col-xs-12 col-md-4 side">
      <form role="search" method="get" id="searchform" class="searchform" action="<?php echo esc_url( home_url( '/' ) ); ?>">
        <div class="form-group">
          <input type="text" value="<?php echo get_search_query(); ?>" class="form-control" name="s" id="s" placeholder="<?php printf( _e( 'Search', 'zaxidna' )); ?>" />
          <button type="submit" id="searchsubmit" class="btn"><span class="glyphicon glyphicon-search" aria-hidden="true"></span></button>
        </div>
      </form>
     <?php get_sidebar(); ?>
    </div>
  </div>
</div>
<?php get_footer(); ?>

functions.php:

<?php
if (!function_exists('add_scripts')) {
    function add_scripts() {
        wp_deregister_script('jquery');
        wp_enqueue_script('jquery', '//ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js', '', '', true);
       wp_enqueue_script('jq', '//s7.addthis.com/js/300/addthis_widget.js#pubid=ra-5852c94376ed1e7c', '', '', true);
        wp_enqueue_script('bootstrap', get_template_directory_uri() . '/libs/bootstrap/js/bootstrap.min.js', '', '', true);
        wp_enqueue_script('main', get_template_directory_uri() . '/js/js.js', '', '', true);
    }
}
add_action('wp_footer', 'add_scripts');

if (!function_exists('add_styles')) {
    function add_styles() {
        //wp_enqueue_style('bs', get_template_directory_uri() . '/libs/bootstrap/css/bootstrap.min.css');
        wp_enqueue_style('main', get_template_directory_uri() . '/style.css');
        //wp_register_style('font-style', 'https://fonts.googleapis.com/css?family=Open+Sans:400,400i,600,700,700i,800&amp;subset=cyrillic');
        wp_enqueue_style('font-style');
    }
}
add_action('wp_print_styles', 'add_styles');



add_filter('use_default_gallery_style', '__return_false');
show_admin_bar(false);
if (function_exists('register_sidebar'))
    register_sidebar(array(
        'name' => 'Side About',
        'id' => 'side-about',
        'before_widget' => '',
        'after_widget' => '',
        'before_title' => '<h5>',
        'after_title' => '</h5>',
    ));
if (function_exists('register_sidebar'))
    register_sidebar(array(
        'name' => 'Side Widgets',
        'id' => 'side-widgets',
        'before_widget' => '',
        'after_widget' => '',
        'before_title' => '<h5>',
        'after_title' => '</h5>',
    ));

remove_action('wp_head', 'rsd_link');
remove_action('wp_head', 'wlwmanifest_link');
remove_action('wp_head', 'wp_generator');
add_theme_support('post-thumbnails');
add_theme_support('post-formats', array('image', 'video', 'quote'));
add_image_size('desctop', 1519, 570, true);
add_image_size('mobail', 736, 334, true);
function get_ID_by_slug($page_slug) {
    $page = get_page_by_path($page_slug);
    if ($page) {
        return $page->ID;
    } else {
        return null;
    }
}
add_filter('comment_form_default_fields', 'bootstrap3_comment_form_fields');
function bootstrap3_comment_form_fields($fields) {
    $commenter = wp_get_current_commenter();
    $req = get_option('require_name_email');
    $aria_req = ( $req ? " aria-required='true'" : '' );
    $html5 = current_theme_supports('html5', 'comment-form') ? 1 : 0;
    $fields = array(
        'author' => '<div class="row"><div class="col-xs-12 col-md-6"><div class="form-group comment-form-author">' .
        '<input class="form-control" placeholder="' . __('Введите Ваше Имя') . ( $req ? ' *' : '' ) . '" id="author" name="author" type="text" value="' . esc_attr($commenter['comment_author']) . '" size="30"' . $aria_req . ' /></div></div>',
        'email' => '<div class="col-xs-12 col-md-6"><div class="form-group comment-form-email">' .
        '<input class="form-control" placeholder="' . __('Введите Ваш Email') . ( $req ? ' *' : '' ) . '" id="email" name="email" ' . ( $html5 ? 'type="email"' : 'type="text"' ) . ' value="' . esc_attr($commenter['comment_author_email']) . '" size="30"' . $aria_req . ' /></div></div></div>',
        'url' => '<div class="form-group comment-form-url">' .
        '<input class="form-control" placeholder="' . __('Сайт (необязательно)') . '" id="url" name="url" ' . ( $html5 ? 'type="url"' : 'type="text"' ) . ' value="' . esc_attr($commenter['comment_author_url']) . '" size="30" /></div>'
    );
    return $fields;
}
add_filter('comment_form_defaults', 'bootstrap3_comment_form');
function bootstrap3_comment_form($args) {
    $args['comment_field'] = '<div class="form-group comment-form-comment">
            <textarea class="form-control" id="comment" name="comment" placeholder="Напишите комментарий" aria-required="true"></textarea>
        </div>';
    $args['class_submit'] = 'btn'; // since WP 4.1
    return $args;
}
add_filter('request', 'my_request_filter');
function my_request_filter($query_vars) {
    if (isset($_GET['s']) && empty($_GET['s'])) {
        $query_vars['s'] = " ";
    }
    return $query_vars;
}
require_once('wp_bootstrap_navwalker.php');
function my_custom_post_navigation($terms, $object_ids, $taxonomies, $args) {
    return array_slice($terms, 0, 1);
}
if (!function_exists('wpex_pagination')) {
    function wpex_pagination() {
        $prev_arrow = is_rtl() ? '<span class="glyphicon glyphicon-triangle-right" aria-hidden="true"></span>' : '<span class="glyphicon glyphicon-triangle-left" aria-hidden="true"></span>';
        $next_arrow = is_rtl() ? '<span class="glyphicon glyphicon-triangle-left" aria-hidden="true"></span>' : '<span class="glyphicon glyphicon-triangle-right" aria-hidden="true"></span>';
        global $wp_query, $the_query;
        if ($the_query) {
            $total = $the_query->max_num_pages;
        } else {
            $total = $wp_query->max_num_pages;
        }
        $big = 999999999;
        if ($total > 1) {
            if (!$current_page = get_query_var('paged'))
                $current_page = 1;
            if (get_option('permalink_structure')) {
                $format = 'page/%#%/';
            } else {
                $format = '&paged=%#%';
            }
            echo paginate_links(array(
                'base' => str_replace($big, '%#%', esc_url(get_pagenum_link($big))),
                'format' => $format,
                'current' => max(1, get_query_var('paged')),
                'total' => $total,
                'mid_size' => 3,
                'type' => 'list',
                'prev_text' => $prev_arrow,
                'next_text' => $next_arrow,
            ));
        }
    }
}
function trim_title_chars($count, $after) {
    $title = get_the_title();
    if (mb_strlen($title) > $count)
        $title = mb_substr($title, 0, $count);
    else
        $after = '';
    echo $title . $after;
}
if (function_exists('acf_add_options_page')) {
    $option_page = acf_add_options_page(array(
        'page_title' => 'Мобильное меню',
        'menu_title' => 'Мобильное меню',
        'menu_slug' => 'theme-general-settings',
            //'capability'  => 'edit_posts',
            //'redirect'    => false
    ));
    $option_page2 = acf_add_options_page(array(
        'page_title' => 'Общие настройки сайта',
        'menu_title' => 'Настройки шаблона',
        'menu_slug' => 'theme-general-settings2',
            //'capability'  => 'edit_posts',
            //'redirect'    => false
    ));
}

add_action('admin_head', 'moi_novii_style');
function moi_novii_style() {
    print '<style>
/*Стили в админку
#menu-appearance,
#menu-tools,
#menu-users,
#menu-plugins,
#toplevel_page_edit-post_type-acf-field-group
#menu-posts,
#menu-dashboard,
.update-nag{display:none!important;
*/
.update-nag,
#toplevel_page_edit-post_type-acf-field-group
{display:none!important;}
.toplevel_page_theme-general-settings2 .acf-fields > .acf-field {
    border-bottom: #ff0101 solid 3px;
}
</style>';
}
function enable_more_buttons($buttons) {
  $buttons[] = 'hr';
  $buttons[] = 'fontselect';
  $buttons[] = 'sup'; 
  // и так далее ... 
  return $buttons;
}
add_filter("mce_buttons", "enable_more_buttons");