Factory Restore - need to connect existing product key

Had to do a factory restore on one of my laptops - the restore took out the existing Norton Internet subscription I had and reinstalled Norton as a 60-day trial.

 

I have two subscriptions, each covering three machines - all installs have been previously used; my account says no more installs are available. However, several machines have since died and protection is no longer needed. I have no records indicating which machines are associated with which product keys.

 

How do I reconnect with the the account, and how do I remove the dead machines from the account, so I can install protection on their replacements? Thanks!