You know how a bicycle work right? a small gear is connected to a large gear. So the back wheel is spinning faster then you're spinning with your pedals (if you want to see the diffrence, compare old bicycles to the newer bicycles). If you switch to a larger gear, you'll notice you'll have to pedal much harder to reach the same speed.
But you want to opposite to happen, you want a gear to rotate slower then to gear attached. Because you want to have the torque on the servo to be much smaller, so what you want to do is attach a large gear to the servo, and attach a smaller gear to the one attached to the servo.
I hope I helped you out with this