Step 4: Connecting the wires
Mostly, the left one (the first one) is + and the right one is -.
You also can check it using the volt meter.
Now mark your + and take the 9v connector, the red one is + and the black one is -.
Solder them together.
Then take some tape (I didn't find my electric tape, but duck tape will do the job ;) and wrap it around the place where the cables were soldered.