How to Hide the "Z Flakera na Blog" Admin Menu

function plt_hide_z_flakera_na_blog_menus() {
	//Hide the "Settings → Z Flakera na Blog" menu.
	remove_submenu_page('options-general.php', 'z-flakera-na-blog/mzgadmin.php');
}

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

Where do I put this code?