OK, I'll take a stab at step by step. No, I do not mean to play the CD in your car. Yes, you can do that, but then the songs are not being played through your TomTom. The advantage of playing music through the TomTom is that when road instructions come, the TT will pause the song, make the road instruction, then continue with your song.
The TomTom wants the files in MP3 format.
1) In iTunes, convert any songs, spoken books, whatever you want to listen to, into MP3s. In iTunes, use the "Advanced Tab" to "Convert to MP3 version." If this option is grayed out, make sure you have selected songs in your list first. If you have selected songs, maybe iTunes cannot make an MP3 version if the song is protected. In that case, see below.
2) Put each of these into a new Playlist.
2) Attach the TomTom to your computer. When it asks to connect to "Computer" say "Yes"
3) Find the folder on your TomTom that's called "MP3" and drag your songs into this folder.
In iTunes, your MP3s will be in a folder within /Music/iTunes/iTunes Music/
(I don't know exactly what on a PC, I use a Mac.)
If you still cannot find your songs, highlight a song and click on "Get Info" - at the lower portion of the info, it will say exactly where your song is stored on your machine.
On the TomTom, the MP3 folder is named "mp3" (lower case).
If the above is confusing, you can make a folder in iTunes of stuff you want on your TomTom, drag all your MP3s into that folder, and burn a CD of MP3s, then drag those files onto your TomTom.
What I was talking about earlier are the files that have protection. You cannot make an MP3 out of them because iTunes won't let you.
Here's how to get around that limitation:
1) Put all the songs and books you want into a folder in iTunes, then burn a CD as an Audio CD of this song mix. When you click on "Burn Disc" you will be asked what sort of disk you want. Choose AIFF. (Note, you do not need to do this if the songs are already unprotected MP3s. This is just for songs which have copy protection that won't let you convert them to MP3s, or MP3s that won't let you play them on your TomTom due to copy protection.)
2) Now you have a CD with songs in AIFF format.
3) Import these songs from the CD back into iTunes as MP3s. These MP3s will now be able to play on your TomTom (see directions above for getting them onto your TomTom.)
Does that help clarify the steps needed?