Adding tracks to audiobooks

[gigapet]

Hi all, I've just been playing about with iTunes 6 and I've noticed the 'Audiobooks' tab in the browser. How do I add existing ripped tracks to that tab? I've the complete 'Hitch-Hiker's Guide' but it's ripped from a CD and not bought from the iTMS. The reason I want to do it this way is I've just 'discovered' the 'Shuffle songs' function on my iPod and I'm getting pretty fed up with having to skip through the spoken word tracks.