Hello. My name is***** can help you with your question.
All you have to do to redeem a Kindle/Amazon gift card is go to the link that I'm about to provide you and then login under your account and you'll see a complete set of instructions. You'll be clicking on the button there to apply it to your account and you will have a code on the gift card either physical or through email. Just enter that code and click okay and it will apply it automatically to your account. Then when you purchase through your Amazon account you will have the option of using the balance from the gift card to pay for all or part of your purchase. These let me know if you still questions.