How to download Photoshop CS6?

I updated to cs6 in 2012.  I now have a new computer, and I need to download a copy.  I have my serial number.  I have deactivated it on my older computer.  Where can I find a copy of CS6 to download?  (when I bought it in 2012, I opted out of a disc, and had it downloaded via internet.) .  Thank you.

-Bronwen Heilman