Protecting more than one PC

Hey guys,

I'm new here and I'm sure this question has been asked before, but I couldn't find a satisfactory answer through the search function.  I have Norton Internet Security 2010 and according to my products in my account, it only provides protection for one PC.  I wish to protect another PC, so do I just need to purchase an additional product key for NIS 2010 ($39.99)?  Thanks in advance for your help.