Before leaning back the microscope condenser/illumination unit, you must first slide away two sliders on top:

The front part of the enclosure can be removed. First you need to slide up the latch on top. The cover is then fixed only by magnets.

There is a built-in illumination inside the enclosure. Use the footswitch to turn the light on/off. The intensity of illumination is controlled by the knob on top of the enclosure.