You can't. You can only transfer from itunes to the ipod, not vice versa. There is a way to use your ipod as a hard drive to transfer songs from one computer to another but then you can't listen to the songs while on your ipod. Don't know how to do that though, you can look it up at the website.
But my guess is you have the songs on your ipod in audio form, and then you can never move them anywhere else.