1. You will receive a Premium key / Voucher code should look like this: FURK.NET-12-10468-3500845299
2. Login into to your Furk.net account. ( If you haven't account, you just need to sign up )
3. Then access: https://www.furk.net/billing/resellers
4. Put your voucher code in field "Voucher", and click on "Use Voucher"