WHMCS option for subdomain creation issue

Hi so. on WHMCS you have the option to make it so people do not have to buy a domain, but instead you can have it so they get a subdomain of your own domain. So for me it would be - Removed - You can see the option - Removed - But when I place the order, it just says: pending. How do I proceed with this process so it works like all other domains.