If pure OXCE works, then you don't mess with it further, instead go into mod folder you downloaded and then unpacked (do not unpack it in OXCE folder, anywhere but there). You have to repeat the step of copying and pasting files from UFO folder with original game to UFO folder in downloaded mod. Then you run the OXCE from the mod folder.
After successfully doing that, you will be greeted with new tab called "mods" alongside others, that are standard. Click that, pick X-COM FILES, game will restart and you can now play.
"user" folder you should be able to easly spot in the second screenshot I provided, but I don't see a reason why would you need to touch it, since mod folder containts everything but files inside UFO folder.
And since we are here, be sure to read every UFOPEDIA article at the start of the game atleast 10 times. And I'm deadly serious when I say that.