Theme has superfish – how to add supersubs?

Have you tried adding this to the themes functions.php?

 function add_supersubs() {
    wp_enqueue_script('superfish', get_stylesheet_directory_uri() . '/js/superfish.js');
    wp_register_script('supersubs', get_stylesheet_directory_uri() . '/js/supersubs.js','superfish');
    wp_enqueue_script('supersubs');
  }    

add_action('wp_enqueue_scripts', 'add_supersubs'); //

this assumes the supersubs.js is in the js folder of the main theme directory.

You’ll also need to modify the header js to fit supersubs.