This is a very simple catapult, very easy to put together. First, line the holes of the top of the base with the holes in the catapult, orientation only matters on the Rubber Band version of the model. Then, insert the axle. After that, put the axle cap on it, inserting the axle cap pin through the holes, once lined up. Finally, insert the catapult stopper in the bottom hole in the base. Use superglue as needed. The ball is completely optional, enjoy!