I have a 96 s

I have a 96 s 10. I put a cap on my truck and have to install a third brake light on it to make the state happy. I want to tap into the brake lites and turn signals. My lite has a ground, a brake and one turn signal wire. I know I need to run it on both sides. Which wire is the hot wire on the brake lites and the turn signals? The turn signal has 2 wires and the brake lite has 3.
Thank you
Mary