The direction that you have the prop turn is entirely up to you. Once you decide which direction you want the plane to go that is
Seriously though, props are designed to only turn one direction. You reverse the motor if necessary to make your prop spin the way it needs to go. If you really need the prop to spin the other direction, you'll need to find a special "left-hand" propeller. These are pretty rare for electric planes, since it's so easy to reverse your motor.