Mick-
    As I recall, there is a screw on the top left of the sliding door frame
that is to be removed and replaced with a snap.  Then, with the notched
portion of the screen in the upper left corner, there should be a snap that
corresponds with the newly installed snap on the frame.  At that point it
should become self-explanatory.  You just need to know where to begin.  Also,
don't expect a perfect fit.  These screens fit very good, but not great.
    Hope this helps.
Greg
86.5 Camper Syncro WLE