First you put your mouse on account upgrade in the right upper corner and then click user settings. Where it says Got A Coupon?  Enter the code. (Coupon is the same thing as code). Hope I helped :)

The latest one I know is 9F88-B50F-8C87-879E It expires 5-1-11 so hurry! It works! :D

Actually they do o_o. You can buy it at ToysRUs, Ralphs, Kroger, FredMeyer, Food4Less, Vons, and Safeway stores. Thee is one card that costs $10 and it comes with 1 month residency and 300 gems. Hope I helped :) My account is blue star shine.