Joomla, Wordpress and Drupal are different CMS (Content Management Systems) that you can to administrate your game site in an easy way. These softwares are free and available for everyone!
This video tutorial show how to install Joomla from cpanel on your webhost.

This procedure also apply on installation of Wordpress, Drupal and phpBB.

If you need a webhost for your game site, HostForWeb.com offer affordable hosting with cpanel.