How to Hide Gallery Manager Lite Admin Menus

function plt_hide_fancy_gallery_menus() {
	//Hide "Settings → Galleries".
	remove_submenu_page('options-general.php', 'gallery-options');

	//Hide "Galleries".
	remove_menu_page('edit.php?post_type=gallery');
	//Hide "Galleries → All Galleries".
	remove_submenu_page('edit.php?post_type=gallery', 'edit.php?post_type=gallery');
	//Hide "Galleries → Add Gallery".
	remove_submenu_page('edit.php?post_type=gallery', 'post-new.php?post_type=gallery');
	//Hide "Galleries → Settings".
	remove_submenu_page('edit.php?post_type=gallery', 'options-general.php?page=gallery-options');
}

add_action('admin_menu', 'plt_hide_fancy_gallery_menus', 21);
Where do I put this code?