Look at the way of changing the lenses.
As we mentioned, one of the features of this camera is that this has double lens mount.
When detaching the lens, first, extend out the lens with the focusing ring, and then with depressing the lens releasing lever, coincide the red dot on the lens with the red dot on the focusing ring.
When attaching, First coincide the red dot, then do reverse as detaching.
Supplementary lenses are many from wide lenses to tele lenses. (It is Nikkor P F2.8/75mm in the picture.)