Before you can activate the "Super MNC - Turbocross Bundle" you need to install the free to play "Super MNC" game from the Steam Store as follows in your Steam client:
- Click "Store" at he top of the Steam Client page.
- Click in the "Search the store" box (upper right side of the central page) and type: Super MNC
- You can click the magnifying glass icon or press ENTER to show the search results, or just click on "Super MNC, Free to play" which should appear below the text you've typed.
- Click the green "Play Game" button, then complete the "Install - Super Monday Night Combat" wizard to install the free to play base game.
Now activate the "Super MNC - Turbocross Bundle" key in the normal way.