To redeem your code, go to marvel.com/redeem and enter your code. If your code is valid, the redemption process will continue. As part of the process, you will need to create an account or sign in with an existing account.
Once redeemed, you will see your digital comic in the Marvel Unlimited app within the My Library tab. Redeemed digital comics will have a Purchased label next to them, and you can also filter by Purchased comics within your library.