Removing the oven door from its hinges, taking off the inner panel, and replacing the broken glass panels inside are the three main steps in repairing oven door glass. Even if just one of multiple panels breaks, replacing that panel keeps heat from escaping.
Turn off the circuit breaker switch that powers the oven. Open the oven door, and slide a screwdriver between the oven and the top of the hinge locks, flipping the lock toward the open door. If necessary, take the screws out that are just over the hinge openings. Brace the hinges with pencils or small screwdrivers to keep the hinges open. Take the door off the hinges if you took screws out, but if the door has hinge locks, the hinges still connect to the door when you lift it out.
Put the oven door on an old towel, and remove the screws holding the handle in place. Take the handle off, and set it to one side. Take the screws out from the bottom of the oven door, and take the door panel away from the outer frame. Put the outer frame to one side. If the hinges are still attached, take the screws out from the inner panel that connect them, and remove the hinges.
Take the retainer panel out of the oven panel, and put the retainer panel to one side, removing any pieces of broken glass. Take out any whole pieces of glass remaining in the frame panel. Wipe any broken glass out of the inner door panel opening using an old cloth. Put the new piece of glass into the panel, and replace any other pieces of whole glass that you took out. Reverse the disassembly process to put the retainer panel back over the new piece of glass, replace the hinges, and put the inner oven door panel back into place on the outer frame. Reattach any screws that you removed, and then reattach the handle to the door. Put the oven door back in place, and secure the door to the hinges. When everything is back in place, turn the power back on to the oven.