Activation is done on Steam.
By purchasing a product, you get a license key from Metro Exodus or a random game. Metro Exodus drop rate is 89%. By writing a positive review about the product, you increase your chances of receiving a bonus game, which may fall as a gift.
1. You need to download and install Steam (if not already installed).
2. Register a new account on Steam or go to an existing one.
3. Go to the "My Games" section and select "Activate via Steam ...", read and accept the agreement of the Steam subscriber and enter the key received immediately after the payment.
4. The game will appear in the list of games and you can download it from Steam.