Help regarding SAVING something to a folder

I'm trying to SAVE a change I'm making to a MODEL folder of a particular TDS plane in P3d 5.4.   The reason I'm trying to do this is because there are instructions regarding this for TDS planes.  I was affected by the Windows update that made all my TDS planes end up with half wings.  I've been trying to remedy this and I've arrived at an impasse.  The instructions say to SAVE a line to the MODEL file in the original plane.  However, when I hit SAVE, the folder doesn't save it....the SAVE command sends me to a folder on my desktop where I store passwords and other important notes.

How do I make the file accept my change?

Thanks