There are two Propellers for the RANGER. They have exactly opposite pitches. They are not identical. One turns clockwise and the other is counter clockwise. They must be placed on the correct motor, to counter act each others directional torque, so that the RANGER doesn't just sit in one spot and spin. Looking at the RANGER from the rear, Blade "A" is on the Right and Blade "B" is on the Left.
Now you can remove the one screw holding the Fan Blade to the motor. Take note.. that the blade is marked with a letter and an arrow for direction of movement. You must replace it with the exact same Blade as the one coming off. The other blade has the exact opposite pitch on it, so the the RANGER is stable and not just spinning in a circle.