With the help of the main Gearbox, power is transferred from the engine to the rotor that will change the power from the engine and send it to the transmission.
After this process, RPM gets reduced in the transmission from 1000 TO 100 RPM, and the torque will increase.
The transmission will drive a stick that will give the rotation directly to the rotor in the engine. Again and again, the shaft will come out from the transmission to drive directly to the rotor tail.