You want the PTO speed at 540 RPM. I hope that's marked on your tachometer.
As far as how fast your ground speed should be...that's dependent on the circumstances. However, since it sounds like you're new to this, I suggest you go pretty slow. If you don't know the terrain you're cutting...also go very slow.
If you have a manual for that tractor...read it thoroughly. Most of your questions will be answered there. You also may have better responses if you post your questions in the "Other Brands/Equipment" and "Grey Market" forums.