I am not from Laminar Research; just a flight simmer from downunder.
My assumption is the aircraft you are seeking help for is an after thought purchase? Alternatively it is a 3rd party add-on.
I suggest you watch several times and follow the advice given in the following link found at https://www.youtube.com/watch?v=V4RjIxrhkXs from Michael Brown at XForcePC. Michael's business specialises in building PCs for flight simulation, particularly units for X-Plane. Laminar Research recommends this business as the only supplier of PCs suitable for XP in the USA .
Michael initially discusses the merits of purchasing additional aircraft and then goes into detail on the installation. Your purchase has to be "dragged and dropped" into the correct folder. Michael tells and shows how to do it.