Follow these steps to redeem your Amazon Gift Card:
- Sign in to your Amazon account in your browser
- Click on your name at the top left to go to the "My Account" page
- Click on "Apply a Gift Card to Your Account"
- Enter the Amazon Gift Card which you can find under My Withdrawals by clicking on "Show Code"
- The balance has now been added to your Amazon account
Note: You can find the official instructions here.