First of all I dont beleive that # 10 wire will adequately handle 50 amps. In order to get 220 volts you need to have two separate hot legs to the unit. The breaker should make contact with two different hot buss bars inside the panel. I suggest that you have a licensed electrican help you but, at least buy a little electric volt ohm meter and measure the voltage between the lugs on the breaker once you install it. Touch the meter leads where the wires would be inserted into the breaker besure your meter is on a high enough scale to read the voltage required. If the voltage read between lugs is 220 or 230 then the breaker will work; if not and you read zero between lugs check to see if you have 110-120 volts to ground. If you get 110-120 from one leg to ground but not 220 between the two legs the breaker will not work. I would size the wire size depending on the length at least at # 8 because your system requires 50 amps. But to be safe I suggest that you use A number 6 wire. The kiln I'm sure uses those little temperature shut off things. As far a wiring it up, the white wire is Neutral from any hot to neutral you would get 110-120 volts. If you use white as a hot leg you have to identify it with black electrical tape at both ends. I suggets that you go purchase 8-3w/g or 6-3w/g wire and use the red and the black as your two hot leads. Besure the power is turned off to the breaker and if at all possible turn off the main circuit to the house whenever you are working inside the electrical panel. There is enough voltage present in the panel to kill you, so be very careful and turn off the power. Never touch the panel while holding wires or while you have your hands inside the electrical panel. If you can wear rubbber gloves and boots while working with electricity I would do that and wear goggles to protect your eyes from sparks. Even with the cirucit breaker turned off I suggest that you measure the voltage to the breaker lugs you are working on before you touch it to be sure the breaker you turned off is the correct one, and that indeed the power is compeltely off. Again I suggest that a licensed electricain help you.