Step 5: Step3: More soldering
Remove the screw in the middle of the circuitboard in the picture.
You will underneth see the the connection for audio and for power to the box. Note how it is connected.
Drill two holes for the 2 and 3 wire cable. See picture.
Pull both cables through the two holes.
Solder the 3 wire connection to the circuitboard in parallell to the aux connector in back of the box.
Solder the 2 wire connection to the circuitboard in paralell to the power in connector. Please note + and -