I want to connect a desktop pc to my laptop and use the wireless ability of my laptop to give my desktop internet.
That's very easy. I do that all the time. Click the network icon in your panel and open network properties. Select your wired interface and click edit to configure it. In IPv4 Settings, choose Method: Shared with other computers.
That's it. You don't have to do anything on the client (in your case, desktop). Your wireless network is now shared on your wired network. You just have to plug it in :)
All you need is here:
Edit: Bonus - exactly the same problem at ubuntuforums.org - http://ubuntuforums.org/showthread.php?t=363156