You definitely have a microscope for inspection work or the like. You can expect a magnification somewhere in the range 5x to 100x and a working distance of 75mm to 150mm (3 to 6 in). If complete, it should be well suited for SMD PCB.
Are you familiar with microscopes of this kind?
Assuming you are not, try this: At first, set the magnification to the lowest value. The magification is set with the knob that has the numbers printed on it. The numbers are not the total mangification, because the eyepiece also contributes to it. Then, find the focus distance by moving the microscope head up and down in the range mentioned above. If you don't get it focused in this range, something is wrong. If you get a sharp image outside the proper distance range, something is still wrong.
Check the black bottom part: A lens should be in it. If you look at an empty tube, and the first lens is way more up in the microscope, a part is missing.
Did you get the microscope from a working lab environment or from a pile of abandoned instrument parts? If it is the latter, the eyepiece probably does not belong to this microscope, someone just put it there because the tube diameters matched. This is a possible explanation for the small image you see. It is difficult to say how it should be, but 5% of your view is not enough.