Add or Change Domain in Apache2 Virtual Host Ubuntu 11.04

I need to change one of the domain names in an Ubuntu 11.04 server, I tried it and it did not work so that is why I am looking for someone who understands Apache2 to do this for me. Here is my attempt: [login to view URL] Before you bid and so we do not waste each of our time, what is the difference between sites-enabled and sites-available Thanks