Don't cut the pot you don't need. Simply wrap it in tape or shrink wrap it. Then tie it up in the harness with the other wires. Most of the boards have a bottom plastic plate with screw holes that hold it down. You also mount the heat sink for the rectifier that also holds the board. This is in the instructions on page 11 and takes up 3 pages! Don't worry about the motors, just make sure the yellow wires go to the harness on page 23. If one ends up running backwards, you just reverse it.
I think you are not looking at the instructions?
