A.  The parts of the microscope that are used to establish Kohler illumination are shown on an Olympus BHTU microscope.  Equivalent parts are on the Olympus CX31 in roughly the same location. 
B.  The field of view that will be seen during at steps 3-5 of establishing Kohler illumination as described above. 

There is a video tutorial on how to focus and establish Kohler illumination found on the Video Tutorials section of the web page. 

•    Make sure you are in the correct plane of focus then move the slide so that you are not viewing the paper but have a clear space under the objective. (Step 1 on Figure 3).

•    Close the field iris diaphragm (Step 2) to close to its minimum size by turning the disc on the base of the microscope to your right.  Turn the condenser height adjustment knob (Step 3) to bring the field iris diaphragm image into focus.

•    Center this image using the two condenser centering knobs (Step 4). As a check open the field iris diaphragm (Step 5) until its image touches the perimeter of the field of view. If the image is not precisely centered, check that your objective lens has clicked into place properly.  If the image is still not precisely centered, adjust as needed using the centering screws.

•    Move the lever that controls the aperture iris diaphragm just under the stage all the way to the right and then to the left.  What affect does this have on your image?  Adjust it so that the maximum amount of contrast is obtained.  Adjust light level, if necessary, by using the sliding voltage control lever.

The microscopes you are using are parfocal so that you only need to make slight fine focus adjustments between objectives.  If you find that you need to make large corrections when you switch lenses or that you are unable to swing an objective into place without hitting the slide, then you are probably not focused in the correct plane, go back to the 10X objective and refocus.