By the 1950's, passenger revenues on America's railroads had long since passed their heyday. Automobiles were fast becoming an affordable option for the modern traveller, and flight was also steadily gaining in popularity.
Open the Steam client, login and locate the Games tab on the top menu. Click this and then select “Activate a Product on Steam…”
Enter your unique code that's displayed on the 'Orders' page of CDKeys.com and follow the prompts to activate.
Your game is now viewable in the “Library” tab and is available to download/install when you’re ready. You can find additional support for the Steam client here: https://help.steampowered.com/en/wizard/HelpWithSteam