A basic example of how to add_action a custom function into a specific hook location.

freelancer-basic-add-action-example.php

add_action( 'theme_hook_before_content', 'my_custom_text' );
/*
 * Echo some text inside a function and then hook
 * that function into a specified hook location
 * using the add_action WordPress function.
 */
function my_custom_text() {
	
	echo 'Hello World!';

}