How to Hide the "Car Route Planner" Admin Menu

function plt_hide_car_route_planner_menus() {
	//Hide the "Settings → Car Route Planner" menu.
	remove_submenu_page('options-general.php', 'car-route-planner-config-page');
}

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

Where do I put this code?