As you turn one gear, the others will turn.  All four gears need to be put together vertically before installing into the square.  And I made an installation tool to help do this.  It is included in the files.

This is a hefty key chain fidget.

 I only had one extra gear to put in the picture of the installation assembly tool. You need to install all four gears into the assembly tool before placing the gears in the holder.  After the gears are in the holder, insert the pins.  I needed super glue on only one of the pins on the outside edge.

Suprise: i found that if I use just two pins, the system turns more smoothly, and everything is still retained in the box.