Used ipod, itunes trouble

Hello,
I recently bought a used ipod from a friend. I brought the ipod home to connect to the computer and download MY music from itunes to the ipod. Since I already had an account with itunes for an ipod that i had lost, it would not recognize the "new" ipod or let me do anything further with the "new" ipod. How do I delete the information from the ipod I lost, and enter new information from the "new one". I don't have any paperwork for the "new" one since I bought it used from a friend. I just want to be able to use the ipod with itunes as simply as possible..help! Thank you, Stephie.