You may have to configure your wireless interface. Personally I have never done that. They probably both need the same workgroup and the same frequency. I think with wireless you may have to use some software to turn your wireless on on one computer, and then have the other computer search for it. If you are not using encryption they may find each other. May have to deactivate a firewall or set up a specific method to allow the connection.
Personally I have never used wireless and dont know much about it.
You might be able to set one up as the server and have the other computer search for it. There is probably some help files in your wireless menu or something that came with the computer with some instructions. You could always look for the wireless software and see if it has a setup to activate it. It may not always be on by default.
Personally I would buy 2 wireless computers unless I planned on using them for that. If you dont have any directions maybe some networking websites can help. Most computer manufacturers have manuals for their computers online. Try a search for your computer with the manufacturer and model information, and download the manual from the manufacturer.
Also go to the networking and Internet foumn category and ask there.
http://forum.pcmech.com/forumdisplay.php?f=15