If you have sufficient rights to add another domain (that's already been registered) to your Plesk account, here's what you can do:
If not, and you would like to become a reseller, let us know.
Plesk Control Panel:
1. Log in to your Plesk control panel (https://login.xpcwebhosting.com:8443) If you have issues with this just let me know.
Adding the Domain:
2. Click the "Add New Domain" button.
3. Enter the domain name.
4. Set the template to "XPC Domains Bronze". (These are just simple limits so the domain can't use up all your resources.)
5. Press OK.
Hosting Setup Screen:
6. Set the login and password for FTP access.
7. Tick the services (at the bottom) you would like to run. If you don't understand this part, just skip it.