: Direct the launcher to your existing Call of Duty: Modern Warfare 3 game directory.
That’s a different game (MWIII, by Sledgehammer/Infinity Ward). The new MWIII does have a developer console for players either — command input is limited to chat or keybinds for certain actions. : Direct the launcher to your existing Call
Create or edit an autoexec/config file
Turn off third-party software overlays (such as Discord, GeForce Experience, or Steam Overlays), as they can intercept input commands intended for the game engine. If you want to customize your setup further, let me know: Are you playing the 2011 classic or the modern reboot ? or Steam Overlays)