Where did you purchase it from? How much did you pay? Typically most users purchase it and either have a redemption code which you submit to get the serial /registration number, or the serial # is found on a sticker attached to a dvd or attached to a card insert- and will begin with 1057 for photoshop elements.
You download install it, and register it- then it will show up in your Adobe account.
If you purchased it from a site like the windows store you need to contact them with any support issues.