[Sharlikran]

The game does not need to be on the C drive.

For addons you will have to uninstall things from the C drive and move them to another drive that is not part of a cloud service. SSD, network or external drives are fine. The game will probably not be able to handle having the addons folder on another drive.

As for the question about how to make the folder, once you have sufficient space then the game will create it. Make sure you do not have OneDrive installed or active. If you do move everything from it to the M drive and uninstall or deactivate it. If you don't I doubt you will get this working easily and without issues that we won't be able to help with.