How to Hide the "cbnet Ping Optimizer" Admin Menu

function plt_hide_cbnet_ping_optimizer_menus() {
	//Hide the "Settings → cbnet Ping Optimizer" menu.
	remove_submenu_page('options-general.php', 'cbnetpo-settings');
}

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

Where do I put this code?