If you use a manual exposure electronic flash, you'll find a settings table (film speed, distance, aperture) at it. Set the appropriate aperture on the Smena.
With an automatic exposure flash set the film speed and then the range you like and set the resulting aperture on the Smena or vice versa.
As shutter-speed you can chose any you like. The longer the shutter speed the more effect (if any) the ambient light will have on exposure.
Look out for book shops in Wales...
(That spool thing though was really tricky, most Apuggers would have wondered too.)