I have just used Garage Band for the first time and come across the same problem.
I have recorded one side of a cassette tape using the software. I split (Cmd T) the 29 minute 'song' into the 8 or so actual songs on the cassette tape and then selected 'Share', 'Send Song to iTunes'. When iTunes finally opened, all I had was one 29 minute song.
So how do I make it into 8 songs in iTunes?
Thanks