1. Please login into your iPithos.to account first: http://www.ipithos.to/login.html
( If you don't have a iPithos.to account, you just need to sign up )
2. Make sure you are logged in.
3. You will receive a premium key / coupon that you can exchange here: http://www.ipithos.to/?op=my_account
4. Please enter your premium key in "Apply Premium Key:" and click "Apply"