How do I fix the brake light wiring in my 1987 toyota camry?

You have a loaded question there because you have not been specific as to what your problem is. However, I will cover a number of symptoms. First off, I have had very few Toyota's show up in my shop with electrical problems in reference to wiring. As far as your brake lights are concerned: if they don't work at all check the fuse. Try the hazard flashers because they energize the brighter element of the bulbs which are the same ones which are energized when you step on the brakes. If they flash that tells you that you have good bulbs,and good grounds back there.
If the fuse is good (and you might try swapping one out with another one that is of the same rating because sometimes a fuse can look good and still be bad (they can have a hair line crack across the fuse. If everything has checked out as good so far, the next step would be to check the brake light switch. If your brake lights stay on all the time, either the switch has backed off from where it was screwed into the housing it was secured to and the brake pedal will no longer press the switch in to open the circuit and turn the lights off. On some cars, the brake pedal has a place where a nylon button is inserted into a hole located in the brake pedal which will push the brake light button in when the pedal is released. If this part is missing, you will just see a hole in the bracket on the pedal where it would push the button in. If everything is intact, unplug the brake light switch and see if the brake light s go out. If they do, you have a bad switch. If your problem is that the lights won't come on when the pedal is depressed, jump the plug which connected to the switch with a wire or paper clip and see if the lights come on. If they do this is a confirmation that the switch is bad.I can go on with more in put, but this should cover a lot of ground on the most common issues found with brake lights which either stay on all the time or don't come on at all. One other note. If the lights do no flash when you turn the flashers on, do not discount the possibility that you may have bad brake light bulbs. I have seen this occur as well.
Good luck