How do I add a new full domain to my special account? I don't want it to be a subdomain.

To add a domain to your web site:

1. Click on the Addon Domains button on the home page.
2. Enter the domain name in the New Addon Domain field.
3. Add the directory that the addon domain points to in the Username/directory name field.
4. Enter the password for the domain in the Password field, if required.
5. Click on the Add button.

Is it possible to change my account from fantasiaparty.net to btwebs.com?

Done.