I got 2 free incubators from an older neighbor today who is getting rid of all his chicken stuff. They are both styrofoam-type models with two windows at the top and hold around 50 or so chicken eggs. One incubator has a forced air fan and an egg turner, the other one is a still-air. I have no idea how to use the egg turner since I've never owned one and this one did not come with a manual. Can someone tell me what to do? Thank you!