Here are the Assembly Instructions:

1) Firstly, place the biggest gear (30teeth) on the second axle of the main body.

2) Then, attach the first and third gear as shown: (first single gear with the whole at the bottom most axle, and the third gear with 26teeth of the bigger gear)

3) Next attach the handle to the side hole of the main body, and lock the handle with the cylinder lock (highlighted as blue in the image)

4) Then attach the connecter's one side to the handle bottom hole, and the first single gear's whole. Also lock the connecter to the handle with the connecter cylinder lock (as highlighted as blue below).

5) Now attach the cover body to the main body by attaching all the screw-like joints together.

6) Lastly, add the propeller with the gear (single body) in the axle and the hole of the cover body. Align the gear with the other gear connecting to it.