Use your activation code to download the game from EA App.
SimCity - Cities of Tomorrow
If you do not have an account with EA app (formerly Origin), you can download the client from the official Electronic Arts website and install it on your computer. When the installation is complete, follow the on-screen instructions to create an account. Then go to the "My Game" tab in the EA app client and click "Add Game" at the top of the page. When you enter your activation code, you will finally be able to download your game, which will automatically be added to your game library.
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