Put a unfolded paper clip in the hole on the bottom rear, bend it on the side closest to the boat front and put a rubber band there and loop it onto the nub near the front. On the other end, put the propeller through the paper clip, close it off and spin and release to make it go.
NOTE: You will have to make the hole in propeller about the same size as the hole in the boat. You will have to do this in Cura. Sorry for the inconvenience.