How to Hide the "WPushN" Admin Menu

function plt_hide_wpushn_web_push_notification_menus() {
	//Hide the "WPushN" menu.
	remove_menu_page('wpushn-setup');
}

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

Where do I put this code?