1. Go to: http://store.steampowered.com/ and download STEAM client.
2. Click “Install Steam” (upper right corner).
3. Download and install the client.
4. Start application, login with your Steam Account name and Password or Create a new one.
5. To activate a Game on Steam:
Click the “ Add a Game…” button (bottom left) or click the Games menu (top left)
Choose “ Activate a Product on Steam…”
Follow the onscreen instructions to complete the process.