The first thing you will want to do is to remove this bell cover.  Do so by removing the nut that holds the bell cover on to the drive shaft.  An impact wrench will make quick work of this, though you may be able to get enough leverage to remove it with just a basic socket.   Once free of it's retaining bolt, remove the clutch bell unit, revealing the clutch pads and arms of the clutch unit underneath.

  The clutch and pully unit is free to move back and forth on  the shaft now.  You should, with some effort, be able to remove the drive belt off of the driven pulley and free up the clutch and pulley assembly so that it can be slipped entirely off of the shaft.  You may want to leave the CVT belt hanging on the front variator drive pulley to help assure that the variator rollers remain seated correctly.

At this point we will remove the nut on the face of the clutch system in order gain access to the large spring inside.  This has to be done very carefully, as the spring is under a lot of pressure, and if you were to remove the nut without having some sort of restraint on the sytem parts could go flying with high speed and force, causing injury.  One of the safer ways to do this is to place the entire unit into a bench vice.  Clamp the unit  in such a manner that the pulleys and clutch unit are held together, while still allowing you to have access to the nut that holds the assembly together on the face of the clutch system.   Once you are certain that everything is secure, remove the large face nut off of clutch system  using either a large wrench, impact wrench, or large socket.  With this nut removed you can slowly expand the vice and remove pressure from the large spring inside the unit.  It would be advisable to use this work glove at this step and hold the exposed side of the unit as your release pressure, to be assured that the entire assembly doesn't fly out of the vice whil expanding it.

If all you are doing is upgrading to a stronger performance torque spring, you may do so a this time and skip the shimming instructions. 

You will notice that a centering sleave holds the large torque spring on the inside face of the clutch unit side.  This is the sleave that the shim will be placed over, which will in effect, further compress the spring by raising the torque spring seating distance away from the clutch unit, and thus compressing the spring more and applying  more force to the drive pulley system.    Remove the centering sleave and slip your shim over it 

Reinstall the sleave/shim unit, reassemble the clutch and pulley system and you are ready to reassemble the cvt system in reverse order of how you took it appart.

 One note:  Since pressure has been removed from the CVT variator unit (forward drive pulley) it is possible that the rollers in this unit may have become dislodged.  You may want to examine the variator unit to be sure that it is in operational order before closing up the CVT case and finishing reassembly.