1. Please log in to your Real-debrid account first: https://real-debrid.com/
( If you don't have an account, please register a new account )
2. Premium key / Premium coupon can be used here once you are logged in to your account:
Access https://real-debrid.com/voucher
3. Paste your Premium key / Premium coupon in "You have a reseller's code ?
4. Choose "24instant" or "Utops.us" for question "What is the origin of this voucher?" and click "Convert" to proceed.