At the end of the game (Operation Blood Storm), the credits will begin to roll. As the credits appear, you will have 8 on-screen prompt option to press using the D-Pad and ABXY buttons. You will have to listen to all 8 letters during the credits. The letters last about 8 minutes while the full credits are about 15 minutes, so you'll have plenty of extra time. You'll also be able to access the credits again from the menu after completing the game.