Here is the method that an old time builder gave me and it seems to work satisfactorily-installing canopies is challenging.
First off on most canopies there is a light scribed line above the flange. Trim the canopy close to this line and then drag it on a sheet of sandpaper on a flat surface, until it is flat-if fuse is not flat you will have to sand it on the plane to get correct contour. Position canopy in correct position and mark. Use a T pin to stick holes in covering just inside the line all around the perimeter. This allows the glue to penetrate down to balsa but holes will not show once canopy is installed. I use Formula 560 canopy glue, it is white but dries clear. It holds once dry but takes 24 hours to completely cure. Put a small bead of glue on edges of canopy, keeping the bead to inside if possible. Position canopy and use masking tape to hold in position until the glue dries. Easy clean up with a Q tip and water. Get all excess off, it dries clear but leaves a film on monocote. Make sure you have a good fit before gluing, don't try to use the masking tape to pull canopy in position. Wild horses can't pull one off if its done correctly and you will get a good seal all around the perimeter. Various shapes of canopies may require some variation from this method, but you get the general concept of installation. Good Luck.