press the green plastic button to open the side of the case
the plastic bezels that cover the drive bays are held in place by a plastic tab.
gently pry up the plastic tab far enough to release it from the frame.
at that point, gently swivel the bezel out and towards the other side of the frame, there are plastic hooks on the other side of the bezel that latch into the metal frame. once you have swiveled out the bezel far enough, they will come loose from the metal frame and can be easily removed.
there will be a metal cover over the drive slot, held in place by two screws. these screws also hold the drive tray in place.
remove the two screws, then the metal cover, and you can slide out the drive tray.
put the jaz drive into position, and screw it in from the underside of the metal tray.
slide the drive back into the machine, then connect the SCSI cable and power.
you may want to reconnect the machine and test the jaz drive, before you put everything back in place.
if you do not have a jaz-shaped metal cover for the jaz drive, it is ok to use the drive without one.
i highly recommend being as gentle as you possibly can when it comes to the swiveling/removing the bezel. the latching tabs on the right side of the bezels are the most commonly broken part on these machines, and no amount of glue will ever make it sit right in the frame again. And especially on machines of this age, the plastic is bound to be brittle.