To activate your key on Battle.net, please follow the steps below:

1. Log into your Battle.net account here.
2. Please select \"ACCOUNT\" at the top bar of the webpage
3. Please select \"Games & Codes\" and click \"Add a Game Key\":

4. Please enter your Key here:

5. Make sure the key is entered correctly and confirm by clicking \"REDEEM CODE\".
6. Done!

After successfully redeeming the key the game gets activated and permanently bound to your Battle.net account.
It then can be found and downloaded within your Battle.net account at any time: