Brilliant, thank you!I'm not going to tell you "Steam Library."
You should have downloaded a single file with an RFX extension, which is a RealFlight Archive file.
If you're using the ESC menus, go to "My RealFlight", then "Import" and then "RealFlight Archives". If you turned on the legacy menu, go to the "Simulator" menu, then choose "Import", and then "RealFlight Archive (RFX, G3X)..."