Demo account / unable to add a domain to service

I’ve recently adquire a Happy Hosting, Im currently on the free trial, and I need to add a new domain redirection.

Every time I try to add my domain, I get the message:

You can’t add that domain: you don’t have permission to add

Is this because im on the trial, if it is for that reason, how do I make my payment in order to enable adding domains

I’d love to look into this for you! Can you give me your account ID number or WebID and the domain you’re trying to add?