1) Remove one of the small concentric pieces that came with the prop, one that fits securely over the motor.
2) Push the piece you selected in step 1, into the prop.See image of original prop and one with the piece inserted.The one with the piece inserted has a smaller hole.In the image, the prop on the top has the piece inserted.
3) Place the prop on the motor, and use rubber bands.Tie the rubber band from one screw to the other , and the prop in between. Tie one on each side of the prop.