I've turned file sharing on both my Macs here at home. One is an iMac, the other a MacBook Pro. I'm sure there's more to it but I can't seem to figure that out. Both are internet connected through WiFi.
I guess your question is how exactly do you share files. To access the shared files just:
Just so you know, when you enable the File Sharing, beneath the green light, the exact URL of that computer will be shown. The
If you are using Lion, or later, Airdrop is, by far, the best option for file sharing. It requires no setup nor special settings, and it sends the files wirelessly, without having both Macs to be connected to the same Wifi network.