Its really simple, Just, U made ur site, Now, Go to manage sites, Remote data, Then u choose web ftp, And put ur name server, Username and password, Then u make a test, And its done.
If u dont understande me, U can view this tutorial.
I was confused about this too -- thinking the FTP should just be x10hosiing.com since my site was a sub-domain. But it is the whole thing: ftp.webdemo.x10hosting.com
m problem wasn't that....see, i uploaded it as said but then when i visited the site it still showed the defaualt page that x10hosting shows (this page is available for purchase or smth like that.....
If you are using dreamweaver to upload your files(easiest way to up load)
make sure that all your files images etc are within the folder /public_html so that your content would be seen online.