You log in / register from the link, you wait 2/3 business days to get off the waiting list, and you complete the course by answering some questions and downloading an application.
Click on the Coinbase referral link then create your account and you can start using coinbase and buying bitcoin, ethereum and litecoin. The 10$ coupon code will be automatically added to your wallet once you have trade more than 100$. You can share you coinbase coupon link & coinbase voucher to invite your friends and get 10$ of free bitcoin when they activate their account.