tw_ee_filter_the_content.php

<?php //Do not include the opening PHP tag if you already have one


add_filter( 'the_content', 'tw_ee_filter_the_content', 1 );
function tw_ee_filter_the_content( $content ) {

    // Check if we're inside the main loop in a single espresso_events post.
    if ( is_singular('espresso_events') && is_main_query() ) {
        return '<h3>Course Details</h3>' . $content;
    }

    return $content;
}