Installed LED Taillight Bulbs, Have question

I installed spider led bulbs in my 2001 Solara to replace the brake lights. Work fine but now I have the warning message on the dash that bulbs are out in the back. I know I have to install resistors, which wires do I tap into, since there are 3 in the wiring harness going to the bulb. I know one has to go to negative, which positive one? Thanks