As summarised above the clutch cable pulls on an arm, which rotates a nut on a five start thread. This pushes a boss on the end of the clutch which connects to a pressure plate on the opposite face of the clutch. Therefore this is moved away from the main clutch body, relieving the spring pressure on the plates.
If your clutch is not releasing properly make sure the arm is set correctly as per the manual. After that it is just a matter of routine cable adjustment