how do i change third brake light on my toyota

First I would see if you can see any light bulb socket in the back of the trunk(located on the top). Most likely you will need to get in the back seat of the car and attempt to take off the 3rd brake light cover by pulling out both sides of the cover while at the same time outward pulling the cover assy. back. I understand it sounds really hard and through my 8 years experience I still have a hard time doing this job. Good luck and I hope this helps