Activating a Blizzard Gift Card key is really simply, just follow these steps:
2/ Log into your Battle.net profile.
3/ Put the code into the code redemption box.
4/ You will see a confirmation message afterwards. Subsequently, the credits will be added to your Battle.net Balance funds.
That's it, your account has been updated!
The key is not working
If you have activated the key according to the guide but the code appears not to work, please check what type of error message you receive and depending on it follow the appropriate instructions: