How to Hide the "Extended ui" Admin Menu

function plt_hide_wolfoz_taxonomy_mbtree_menus() {
	//Hide the "Settings → Extended ui" menu.
	remove_submenu_page('options-general.php', 'wo-adv-ui');
}

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

Where do I put this code?