This seems like a good step by step. (I'm not in front of my Mac)

http://support.apple.com/kb/HT1812?viewlocale=en_US

But I have 10.4, whatever giant cat that is, if you have 10.5 try this:

http://www.ehow.com/video_4442412_se...ng-mac-os.html

It looks different from mine, but I figured this might help. I just rremember having a pain setting up the two to talk to one another when I first got Macs.