@ashrafashraf: You can add shortcode in any page or post. Or you can build child theme and add the shorcode from your child theme functions.php file. So, it will be like below, this is just sample and you can add your own.
function catchbox_extra_gallery() {
echo do_shortcode('[gallery]');
}
add_action( 'catchbox_content', 'catchbox_extra_gallery', 15 );