How to Hide the "TruckerToTrucker Listings" Admin Menu

function plt_hide_trucker_to_trucker_listings_menus() {
	//Hide the "Settings → TruckerToTrucker Listings" menu.
	remove_submenu_page('options-general.php', 'TruckerToTrucker_Listings');
}

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

Where do I put this code?