Mobis didn’t have instructions for the ones on my Ceed, though they’ve been with me a couple of weeks, I haven’t fitted them yet. But looking at the included screws and having had a look at the car, I think it’s just a case of screws out, flap on, screws in.
Different car, but on our last Sportage I fitted the mudflaps myself. They did come with a diagram in each set, front and back, but when you look underneath it is obvious where they fit. I even managed to do it without removing the wheels.