L5740 HSTC and JD model 390 Flail Mower

Seeking advice, the Flail Mower does not have an overriding clutch in the gearbox nor on the PTO driveline, should I install an overriding clutch on the driveline. If so, would the type at the local farm supply store which attaches to the tractor PTO do the job? This is first time to use the mower and I don't want to damage the tractor or the mower.
Anyone have any recommendations?

Thanks for info. Roger, since I initially posted, I did some research and determined how to turn the tractor PTO by had to determine if it has an internal overriding clutch which most likely it does.
How do you like the 390 flail mower ?
thanks
Sam