Step1: Remove the casing, taking care not to lose the screws and remember where the gears were. If it is held together by stickes, rip them off. You can use sticky tape later on.

Step2: Plug your servo into your receiver, where the diagram shows:

Step3: Turn everything on, and move the control stick on the transmitter up and down, and the servo should turn in opposite directions, and when you return the stick to the normal position, you want the servo to stop. so adjust the potentionmeter that the final gear rests on, so it stops moving. Glue it into position.

Step4: Remove all of the stops, which are plastic blocks that stop the gears from turning, but be sure that it is inline with the rest of the gear.

Step5: Drill a tiny hole in the connecting plate to the final gear, so it can turn freely on the potentionmeter shaft:

Step6: Put it back together