Unplug the oven. Make sure all the oven controls are set to "off." Open the door of the oven. Slide out the oven racks. Remove the two screws at the rear of the oven bottom. Slide your fingers under the slots on either side of the oven bottom and lift up the bottom. Push back, then lift out and set the oven bottom aside.
Examine the existing igniter. Note which color wires on the igniter are connected to which color wires at the back of the oven. You may find it helpful to take a picture of the wiring to guide you.
Remove the two screws that hold the igniter in place. Loosen the wire nuts and disconnect the two wires running from the igniter to the stove wiring. Lift out the igniter.
Slide the new igniter into place. Connect the two wires on the new igniter to the wires in the oven. Use the new ceramic wire nuts that come with the new igniter.
Plug the stove back in. Turn the oven knob to 250 degrees. Wait two minutes. Your igniter should begin to glow red, and you'll hear the gas come on. Turn the oven off.
Replace the oven bottom. Slide it back into place and replace the two screws.