How do I install Norton Internet Security on a Second computer?

2 years ago, I ordered my comp from HP with a 3 year subscription of Norton Internet Security for up to 3 computers, my girlfriends computer is currently running off of free trials, and is running like hell. I looked around on Norton's site, and all I'm able to find is how to purchase. I have my Keys, I just can't find a download.

2 years ago, I ordered my comp from HP with a 3 year subscription of Norton Internet Security for up to 3 computers, my girlfriends computer is currently running off of free trials, and is running like hell. I looked around on Norton's site, and all I'm able to find is how to purchase. I have my Keys, I just can't find a download.