You would typically need a utility like WinRAR or 7-Zip to open it.
If the file is a tutorial for ILS (Instrument Landing System) landings, here are the standard steps to follow in most simulators: Filedot ILS Land Ufo 018 rar
Look up the ILS frequency for your destination runway (e.g., Runway 18) using the in-game map or a chart. You would typically need a utility like WinRAR