How to activate Katfile Premium Voucher:
1. You will receive a Katfile premium voucher like this: 7999xxdlnd5774la
2. You should be log in : https://katfile.com/login.html
( If you haven't account at Katfile, you just need to sign up: https://katfile.com/?op=registration )
3. Make sure you are logged in. Then access this link: https://katfile.com/?op=my_account
4. Put your voucher code in field "Apply Premium Key", and click on "Apply"