By hand or with a arduino code. The servo and the mechanics has to be both in the middle position.

#include <Servo.h> Servo myservo; void setup() { myservo.attach(A2); } void loop() { myservo.write(50); // set servo to mid-point delay(2000); myservo.write(90); // set servo to mid-point delay(8000); myservo.write(1400); // set servo to mid-point delay(2000);

This needs to be done carefully.