Launch the Battle app. Log in with your Battle account email. Select Call of Duty: Modern Warfare. Select the content you wish to install: Campaign, Multiplayer, Special Ops, Survival or Warzone Caldera.
How to Preload Call of Duty Warzone 2 on Steam. Launch Steam and search for Call of Duty Warzone 2. On the Call of Duty Warzone 2 store page, scroll down to the Preload Call of Duty Warzone 2 section and click "Pre-load Game".