Unless it's rusted, it should turn fairly easy. A flying buddy of mine did have one where the threads started to flake off the shaft though and it got real hard to turn. He had to replace it. (the threaded shaft part) Jim Chuk
I have one (and am fairly glad with'm): the central shaft should turn easily. You can put a screwdriver through the hole of the shaft to help it, though.
maybe you need to loosen the big nut a half a turn and then put something like a small screwdriver in the big shaft and turn it. not sure which way changes the prop. will just have to look at the blades for flat or more pitch for that one. you need more flat. I have the electric motor in it's place so I just flip a switch.
Exactly as Slyfox said: turn the shaft clockwise and you'll get more angle of the blade... Easy does it! Beautiful system - specially when you've seen people cursing and trying and struggling with their prop - to get all three blades the same angle: in one word fabulous!!