Head to
www.x10premium.com and purchase a new account; there's two ways to get the data and whatnot copied over once you've got the paid account.
The easiest way to move the data then is to use the link to the clients ticket area (you'll receive it after signing up - it's COMPLETELY separate from the free one and much faster response time), and open a ticket requesting the account data be moved from your free account to the paid one. To speed the process, please include your cpanel name and the server you're on - that'll ensure they don't have to ask you for it when they look at it
The harder way but preferred by some is to take a backup of your free site via FTP and PHPMyAdmin, and import the data/reupload it to the new paid account. Depending when you get the paid account this might be quicker as although there's staff who are sometimes on overnight, it's usually slower response times than if you request it during the day.