I didn't have instructions. I was trying to connect an amplifier board to the Raspberry Pi. I decided to solder the wires of an audio jack to the amplifier board, and then plug the jack into the 4-pole AV port of the Raspberry Pi. The issue I faced was determining which wires to use from the audio cable.
I sought help here, and used your suggestion about using my multimeter to trace the wires. Unfortunately, after soldering the audio jack to the amplifier board, I was unable to get the speaker to output sound. I decided to see if it was possible to solder directly to the Raspberry Pi, and I found some instructions that showed me how.