Hey there!
The userSetup.py is not a plugin, but rather a python file that needs to go into your maya/scripts folder. That’s all you need to do. Once you open Maya, it will ask you where the tools directory is, and then you point it to the location on disk, and you’re off to the races! There is a video up above I made. It should be valid still, though it was recorded on Windows.
Cheers!