Position the remaining half sphere under the head of the attached bolt & then press the top half into place. You will now have 5 closed spheres; 4 of which are attached by one bolt to the central sphere. Repeat each of these steps to make the top or bottom layer.
If you then hold the central sphere of the top/bottom layers firmly between thumb & forefinger & with the other hand, hold one of the attached spheres & rotate it clockwise a few turns, you should be able to tighten the nut-bolt assembly further. Repeat this with the remaining spheres & when done place the 4 sphere layer on top of one of the 5 sphere layers & then put the other 5 sphere layer on top of the 4 layer.
Click on the Details Tab below for assembly instructions.