I had tried what you suggested and it gives me an error on the Cpanel it won't let me add on a domain it says you cannot add this domain it is taken from the total 0 or something like that. Is the domain going to be registered though hostony or another company the domain I want to register is zerodesigns.com . Thanks for your help.

What plan do you own? Profi?

Yes I think that's the one is their a way I can buy an addon domain?

Yes you can purchase additional domain hosting for $3.95/mo or upgrade your hosting package to higher plan which includes more domains.