OK, I know from searching here that I can renew an existing NIS 2010 installation by purchasing a retail boxed version and using that product key. I also found that I should wait until the existing subscription is within a day or two of expiring since I will lose any remaining days.
What I can't find is where to enter the new product key to extend the subscription. Can I do this within my existing Norton account, or do I have to create a new account?