Welcoome to x10 CharlesHong!
Basically for hosting, cPanel is the place to go to change some hosting settings and to see how much bandwidth and disk space you've used. It's also the place where you can edit your site quickly and upload files. You can upload your files using an FTP client, and by placing your files in the public_html folder. If you want to run a forum, just visit the x10Hosting Account Panel at
http://www.x10hosting.com/account and select Intermediate PHP and state that you want to run a forum or a blog, and you should be all set to go afterwards.
Hope this helps you get the hang of the place. All links to cPanel and stuff are in the account panel on the site.