add new domains to a magento installation

I wish to point some domain names to the specific websites/stores created within a single magento installation, hosted on hostgator VPS, I have plesk control access for you and ftp info as well. Domains from godaddy and else where are already pointing to the server. I have 4 dedicated IPs, will use two different ones for the different domains: [login to view URL] will be pointed to it as well as [login to view URL] - to two different websites within same installation. I will need documentation on the setup/files changed for future upgrades. I just like to have documentation on everything we do. There are already a few websites running on this installation. Should be easy and quick to do for those who know what they are doing.