1. Download, install and run STEAM (you must run and activate the game directly in the Steam application, not your browser).
2. Launch the Steam app and follow the steps to create a new account or log in if you have already created one in the past. Once logged in, click on "Games" in the top toolbar and select the option "Activate a Product on Steam". Follow the on screen instructions and paste the product code you received from KeenShop account when prompted. If the key is written on more lines, every line is one key and each of them must be typed in separately.
3. Once the activation process is completed you will find the game listed in your games library.
Video guide how to activate the game can be found HERE.