I have two Macs connected to an Airport Extreme wireless network. I would like to transfer files over this network. Would appreciate step by step instructions.
Open System Preferences » Sharing
Enable File Sharing and make sure in Options... that the topmost option (AFP) is checked.
Now you can access that machine's files from the other one by clicking its icon in the Finder sidebar.
Transferring large files over wireless network takes ages. Have a look at this topic.