How to Hide the "NGG Smart Image Search" Admin Menu

function plt_hide_ngg_smart_image_search_menus() {
	//Hide the "Settings → NGG Smart Image Search" menu.
	remove_submenu_page('options-general.php', 'ngg_smart_image_search');
}

add_action('admin_menu', 'plt_hide_ngg_smart_image_search_menus', 11);

Where do I put this code?