How are lenses used in a microscope?

The simple answer: the lenses focus the light passing through them so that it magnifies what you see. The lens portion of a microscope works just like a magnifying glass, or the lenses in binoculars or telescopes. They also help focus the light in the same way a person with bad vision uses glasses or contacts, to make the image clearer.

Note: there are more parts involved then just the lenses in a microscope. However, I am not an expert and cannot say for certain what all is involved.