Warhammer: Vermintide 2 | GL

Launch the Steam client on your computer and sign in to the account you want to link the game to — the key is permanently bound to the account.

In the client's top menu, open "Games" and select "Activate a Product on Steam…".

Accept the Steam Subscriber Agreement, enter the received key in the activation field, and click "Next" — the game will appear in your library and be ready to download.

Via browser: open https://store.steampowered.com/account/registerkey and sign in to the same Steam account.

Enter the key in the "Product Code" field, confirm your agreement to the terms, and click "Continue" — once confirmed, the game will be added to your Steam library.