Description
The Complete Master Chief Story – Honoring the iconic hero and his epic journey, The Master Chief’s entire story is brought together as The Master Chief Collection. Halo: Combat Evolved Anniversary, Halo 2: Anniversary, Halo 3, and Halo 4 are all included with Xbox One visual fidelity, 60fps, a total of 45 campaign missions plus more than 100 multiplayer (including the original Halo Combat Evolved maps) and Spartan Ops maps. Along with new prologue and epilogue cut scenes foreshadowing Halo 5: Guardians, this is the collection Halo fans have been waiting for, all on Xbox One.
Steam 
How to activate your Steam key?
1. Open your Steam client. (If you don't have a Steam Client, you can install from here https://store.steampowered.com/about/)
2. Sign in to your Steam account. (If you don't have a Steam Account, you can create from here https://store.steampowered.com/join/)
3. Click “ADD A GAME” button which is at the bottom of the Steam Client.
4. Now select "Activate a product on Steam..."
5. Write or copy-paste your Steam key which you purchased from Gamesforpc.
6. Now your game is in your library.
7. Find your game in your library, select and click install to start your download.