Your FTP address is the same as your hosting address, i.e. if your site was at site.x10hosting.com, your FTP address would be site.x10hosting.com
As for the domain, you should probably add more info, but generally, to add a domain, you should first point its nameservers to ns1.x10hosting.com and ns2.x10hosting.com, then either add it as a parked domain in CPanel, or request a change in the changes forum (just below this one on the index).
