Steam is one of the biggest digital distribution platform developed by Valve Corporation. It let's you digitally manage your games, play mulitplayer and even socialize with your friends and people around the globe via its networking program. Steam has its own store where users can purchase video games and software. It is available on Microsoft Windows, Linux and OS X. Application for smartphones with Android and iOS is also available to download.
Launch your Steam
Locate ADD A GAME option.
Enter your game key.