From the description it looks like the script will take care of everything provided you just load the script. To load the script, you can input the following PHP into custom/custom-functions.php file –
add_action('wp_enqueue_scripts', 'my_enqueue_scripts');
function my_enqueue_scripts() {
wp_enqueue_script('jquery-mediaqueries', get_template_directory_uri() . '/js/css3-mediaqueries.js', array('jquery'), false, true);
}
assuming you will have this script placed in js folder of the theme directory.