How to use diana f+ nikon adapter with fish eye lens?

I got a diana f+ lens adapter for my nikon D40 and a diana lens+ 20mm fish eye lens to go with it. The two fit together fine and snap onto the camera fine but when i take a picture there's no new effect like lomography or fish eye. WHAT AM I DOING WRONG?

A 20 mm is NOT a fisheye.

A fisheye is usually from 6 mm to 10 mm on your D40. I'm not surprised you can't get the effect you expected.

A 20 mm on a medium format Diana camera (120 film) is certainly going to cover nearly 180° but on your fine D40, the coverage is only about 74°, about what you could expect using a 28 mm lens on a 35 mm camera

You seem to be just one more intelligent but uninformed person who has become a victim of slick marketing. Only a good understanding of photographic fundamentals will protect you from these kinds of "snake oil" sales organizations.