The different configurations are selected by switching different cages at the top of the telescope. This is done with a crane.
Prime focus has the camera or eyepiece at the top of the telescope instead of a secondary mirror.
Newtonian has a flat mirror in place of a secondary mirror. A platform attached to the inner side of the dome carries the observer up and down with the telescope. Bent Cassegrain has a flat mirror as its tertiary mirror. This reflects the light out the side of the telescope. Traditional Cassegrains have a primary mirror with a central hole.