@lambdog:
1. First build a child theme. You can create the folder like catch-box-pro-child and create style.css in this child theme. Here goes the sample style.css
/*
Theme Name: Catch Box Pro Child Theme
Theme URI: http://catchthemes.com/themes/catchbox-pro
Author: Catch Themes Team
Author URI: http://catchthemes.com
Description: Catch Box Pro is an advance version of our popular theme Catch Box. It is based on HTML5, CSS3 and Responsive Web Design to view in various devices. Some of the additional features includes: featured image slider, option for full width slider, disable responsive layout, header option for margins, image and search, color options, additional color scheme, font family options, font size options, additional default layout options, additional optional sidebar for homepage, archive, pages, and posts, homepage category setting, more tag text options, and footer editor options. Multilingual Ready (WPML) and also currently translated in Brazilian Portuguese, Spanish, Danish, Germany, French, Polish, Czech, Croatian, Italian, Swedish, Russian, Arabic, Serbian, Dutch, Persian, Hungarian, Slovak and Japanese.
Version: 1.0
License: GNU General Public License, version 3 (GPLv3)
License URI: http://www.gnu.org/licenses/gpl-3.0.txt
Tags: dark, light, blue, white, black, gray, one-column, two-columns, left-sidebar, right-sidebar, fixed-layout, fluid-layout, responsive-layout, custom-background, custom-colors, custom-header, custom-menu, editor-style, featured-image-header, featured-images, full-width-template, microformats, post-formats, rtl-language-support, sticky-post, theme-options, translation-ready
Text Domain: catchbox
Template: catch-box-pro
*/
/* =Import Catch Box Pro Parent CSS
-------------------------------------------------------------- */
@import url("../catch-box-pro/style.css");
/* =Child Theme Custom CSS
-------------------------------------------------------------- */
2. Then create functions.php file and add your advertisement like below:
<?php
/**
* Catch Box Pro Child Theme functions and definitions
*
*/
// Add in Advertisement after header
function catchbox_child_advertisement() { ?>
<!--- You can add your ads code here -->
<div class="leaderboard-ads">
Hello Ads
</div>
<?php
}
add_action( 'catchbox_after_header', 'catchbox_child_advertisement', 10 );