You adjust this one by tightening or loosening the large nut on the gear box side. There would be a certain torque specification given for adjusting this clutch to a specific horsepower rating, unfortunately I do not have that information, so to set this one it will be by trial an error.
Just remember not to over tighten as you DO want the clutch to slip if you hit something solid. A little slippage is way better than none at all.