1. You will receive a Premium key / Voucher code should look like this: 18iijzpu06nytq61
2. Log into to your account.
( If you haven't account, you just need to register free account: http://www.wickedcloud.io/?op=registration)
3. Then access: http://www.wickedcloud.io/?op=my_account
4. Put your premium key in field "Apply Premium Key", and click on "Apply"