Call of Duty®: Black Ops III Zombies Chronicles Edition includes the full base game plus the Zombies Chronicles content expansion.
After purchase it is necessary:
1. Download and install Steam http://steampowered.com/download/SteamInstall.msi (if not)
2. Register a new account on Steam or go to an existing one;
3. Select "Activate via Steam ..." in the "Games" section
4. Enter the code you received after payment.
5. After activation, the game appears in the list of games and you can download it from steam, and then start playing.