First scuff up the inside of the frame with 80 grit or similar, and make sure there are no sharp strands of glass sticking up as these will scratch the canopy.
Various glues work, Pacer I think make a 'canopy' glue which is water soluble, after carefully inserting the 'glass' into the frame clamp it making sure its a good fit all round. There is a neat trick of using magnets to replace the clamps which some builders use.
I tend to lift one edge and run a bead of glue in and then re-clamp until dry, then repeat for the other side. Being water soluble it can be wiped off the 'canopy' if it speads, spreading is a drawback to this glue as its rather runny.
Option two is to use a fast two part plastic epoxy product, same method as before but here glue strips of around 2" or so at a time, leaving each to go off before moving on to the next one.
Its advisable to also carefully scuff the canopy with sandpaper as well, best to trial fit in the frame and mark the edge so you know where to sand to.

marcs