The viewfinder is separated in two. In the right picture, the light blue arrow shows you a viewfinder and the yellow arrow shows you a viewfinder in which you focus some image with the double-image superimposing rangefinder.
Focus roughly with a distanc scale at the right side of the viewfinder.
And also there is a helicod knob at the left-hand side of the lens with which you adjust the focus of a image precisely.
In addition to that, you have to extend the lens to some extent with the helicoid knob when you take pictures, for a shutter won't be released without doing it.