So, for the future wanderers and for future read me files.You must enter the game after installing the updates at least once before installing the mod - there's an additional update process.
A bit shame on me - I should have watched videos on YouTube about this process earlier and saving me the embarrassment.
The read me said copy the folder. Me, coming from a long history of OSes that will overwrite folders that have the same name and not merge them, I renamed the existing folder.
Only today I realized that multi man will actually overwrite only the existing files inside the folders leaving everything else untouched.
So for future Google searches: you have to copy on top of the current folder.
Now that I took the plunge (super scary as it’s opposite as my computer have done for the past 15 years, my windows days are that long gone), everything works. Great fun. Excellent mod. Amazing.