A TOTALLY USELESS VIDEO PRESENTATION ... First the title (HOW TO REGISTER) is mis-named, it should be "How to download, install, and run a purchased product".

At that it does a fairly good job of displaying, however the registration process (valid for this product) does NOT show you how to register a more complex game such as CIV IV, or any of that family of games.  INSTRUCTIONS FOR REGISTERING SHOULD ACCOMPANY THE DOWNLOAD IN A FILE which would be found in the DMG file you receive.  Especially IF the registration process is different from the method shown here!

What that guy said is right, nothing from the CIV family works.