How do I install Addictive Drums 2?

Hi,
 
This is my first post here. I've only had Sonar X3 Producer for a few weeks and I've been enjoying learning it. I have a question though. When I installed X3 initially, I didn't install AD2. I already have Superior Drummer, so I just skipped the AD2 installation because I just wanted to jump in and start creating. However, I'd now like to give AD2 a try, but the problem is I can't work out how to install it. I looked at the installation instructions and it says to the XLN website, enter the product key and download it, but I can't find a product key. AD2 doesn't appear in my Cakewalk account and there's nothing in my email.
 
So after all that, what do I need to do exactly?
 
Thanks in advance.