Umm... I am assuming you know html and have made a few pages for your site. If not, make them.After you have made them, the page you want to be your homepage should be named index.htm, index.html or index.php or .asp as per your needs. This file and all other files you wish to be available to the public should be uploaded via ftp (file transfer protocol) to the public_html folder of your (sub)domain. SmartFTP is a good FTP program, I use that and I don't really know any other so ask someone else abt any other.
Other things you can do include going into cPanel and tweaking everything to your liking... I can't really tell you everything abt cPanel, it has way too much inside it for me to explain and its really simple to understand. But if you don't understand anything of it you can always post back. :kdubb:
The link to your cPanel should've been mailed or PMed to you, however they do it. I dunno, I'm not hosted by x10.