Note that each unit has tabs or flaps (orange) and pockets (yellow).
Prepare six units of the puzzling ornament units as described by Garibi IIan. People familiar with modular origami will be able to assemble the units with no difficulty. But for beginners, it might be easier if you follow the instructions below:
Position unit1 "upside down" so it is resting on its apex. Position unit2 on one of its corners. Connect the two units by sliding in the orange flaps of unit2 into the yellow pockets of unit1.
It will look like this. Rotate half turn so you can work on the other side.
Repeat the above step: position unit3 on one of its corners and slide in the orange flaps under the yellow pockets.
Connect unit4 in front of the model. Again, slide the orange tabs of unit4 under the yellow pockets of the model.
Repeat with unit5 behind the model.
Rotate the model quarter turn. The last unit goes on top like a lid.
Insert unit6 in between the orange flaps. Slide the orange flaps (a and b) under the yellow pockets (c and d) of unit6. Repeat behind as well.
This is the top view: insert the orange flaps of unit6 into the yellow pockets of the model.
Once you have done that, the puzzling ornament is finished! At its current orientation, it is a skeletal octahedron. Can you convert it to a skeletal cube? Take the extra step to fold the edges back to get a star.