In order to add Gift Cards to your Battle.net account, follow the instructions below:
-Go to www.battle.net/balance
-Log in to your Battle.net Account.
-Enter the code into the code redemption box.
-If all goes well, you will see a confirmation message and the amount will be added to your Battle.net Balance funds shortly thereafter.
-Check that your funds have been correctly added by looking at your balance in the top-right of your account management screen.