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.
Load up your Battle.net balance, then use it on Blizzard Entertainment games, character services, in-game items, and more.
Battle.net balance is simple and convenient to use.
Use Battle.net balance to buy World of Warcraft realm transfers and other paid services, as well as digital versions of Blizzard games like Diablo III and StarCraft II.
You can also use Battle.net balance to buy items in games like World of Warcraft and Hearthstone.