Do not listen to bretshark. Any freshwater fish is to big for a 10 gallon aquarium. you would need a 500 gallon tank to keep a school of crappie in. Please for the sake of the fish do not attempt this.
The tank is far too small. I've caught crappies at 8" easy. It will be stunted, and will probably die. If you move him/her into a bigger tank (30 gallons, I'd guess.) I would feed it worms or bug larvae. Since I'm in MN and we have cold lakes, and lots of Crappies, I would say 65 degrees is good for him. But also, I'm pretty sure crappies school. So it might be very upset and die from stress. Good luck, though. I have a friend who has a small mouth bass and some sunnies in his 75 gallon tank.
I'm staying faraway from the ethics of keeping Pomoxis nigromaculatus in a 10 gallon tank, but as far as feeding it goes, I can answer that for you.
Spend some time catching natural food for it, or any wild fish you keep. It will not be used to eating goldfish flakes or pieces of bread. Their natural food will be much healthier for them. You can try shad, minnows, shiners. Some kind of zooplankton, insects, and crustaceans will work also.
Edit:
But in all honestly, you may as well gut it, fillet it out and fry it up... because all you're going to do is kill it in that size of aquarium.
I have had bluegill and pumpkin seeds in 10 gallon aquariums before. The aquarium is too small but I wouldn't worry about it. The right temperature should be 50-65 degrees farenheight. I would feed him fish flakes, brine shrimp, worms, or bloodworms.