3.	While looking through the eyepieces with eyes, open and close the right and left eyepiece tubes until the two circular viewfields fue together into one.  Adjusting interpupillary distance means matching the distance between the right and the left eyepiece tubes with your interpupillary distance.  When the interpupillary distance is not adjusted, you will not enjoy the full performance of the stereoscope and your eyes will get tired while using it.
4.	While looking through the left eyepiece with your left eye, rotate the focusing handle until you obtain a sharp image of your subject in the left eyepiece.