Go to bnet's website and log into your account. Go to manage game and you will see your game there once you bought it.
For logging in part, just log in using your bnet's username and password will do.

There's no CDkey etc involved on this.

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Added on May 19, 2012, 12:30 pmOh, if you've a smartphone, just attach an authenticator for your account.

This post has been edited by Lucifer96: May 19 2012, 12:30 PM