Follow the guide below to change to a Campagnolo or XDR freehub body setup.
The stock free hub can be removed with or without the cassette installed. If you choose to remove the cassette prior to removing the free hub, follow the instructions on 'What cassette can I use on my VOLT trainer?'.
Remove the Adaptor C nut with the 17mm wrench. Set this aside to use again later.
Remove the existing freehub by sliding it off.
If a spacer is supplied with new freehub body, install this now.
Install the free hub on the axle. Twist counter clockwise to help the pawls fall into place. You should not be able to see the pawls.
Re-install the Adaptor C nut removed in step 1.
Torque the nut to precisely 6Nm.
IMPORTANT: Over-torquing the nut may cause damage to the bearings. If you do not have a torque wrench, your local bike shop most certainly will!
Here is a short video on replacing the cassette: