1. Go to:
http://store.steampowered.com/ and download STEAM client
2. Click "Install Steam" (from the upper right corner)
3. Install and start application, login with your Account name and Password (create one if you don´t have).
📝 Please follow these instructions to activate a new retail purchase on Steam:
4. Launch Steam and log into your Steam account.
5. Click the Games Menu.
6. Choose Activate a Product on Steam.
7. Follow the onscreen instructions to complete the process.
8. After successful code verification go to the "MY GAMES" tab and start downloading.