If it is not listed, either launch your Total War game then return to the 3D Settings menu, or select ‘Add’, then ‘Browse’ and navigate to the Steam App folder of your Total War game (commonly “C:\Program Files (x86)\Steam\steamapps\common\ ”) and select the executable e.g. Select a program to customize” and left-click on it. Once the Manage 3D Settings page has launched, look for the executable of the game (.exe) in the drop-down box underneath “1.Right click on the desktop and select ‘NVIDIA Control Panel’ Then click ‘Manage 3D Settings’ (on the left hand side).Ensure that you have the latest GPU drivers from either your Laptop’s manufacturer’s official website or Nvidia’s website.To set a preferred Graphics processor for your Total War game, using Nvidia' Control Panel: