The photographer turns a ring on the lens until two superimposed images are aligned in the viewfinder. Modern lens-shutter cameras tend to have some sort of autofocus mechanism. Without the mirror and prism, lens-shutter cameras can be much lighter and more compact than an SLR using the same film format. With no mirror to slap, lens-shutter cameras are also much quieter than SLRs. The United Nations, for example, requires that photographers use Leica 35mm rangefinder cameras to record events.
Any camera can be a panoramic camera.
Once you get home, use a pair of scissors to trim the big print until it is long and skinny and contains the subject matter of interest. They use the same lens as in normal mode and mask off the top and bottom of the frame. APS cameras do the same thing except that they record the panorama mode magnetically on the back of the film. The entire frame is exposed and you could later change your mind and ask the lab to print the whole frame. You won't get very high image quality if you print from only a tiny portion of a tiny negative.