Locate the 16-digit code on the back of your gift card. (You may need to peel or scratch off the label first).
Open the App Store on your device.
At the top right of the "Today" screen, tap the sign-in button, your photo, or apple.com/redeem your initials.
Tap "Redeem Gift Card or Code." (If you don’t see this, sign in with your Apple ID first.)
Tap "Use Camera" and follow the instructions on the screen to upload the card info instantly. You can also tap "Enter Code Manually," then follow the instructions on the screen to input the card info yourself.