Please check your mail for the code (can check your spam mail as well).
1. Login on the Amazon US website at the following link: https://www.amazon.com/ then select "Profile your account.
2. Select "Manage gift card balance" in the Payment section.
3. Select "Redeem another gift card".
4. Enter the voucher code and select "Apply to your balance".
Your voucher code has been successfully redeemed, enjoy!