Try a search here :
Camera Manuals Online or here
Leica camera instruction manuals, leicaflex camera instruction manual
You find many old manuals and catalogs.
And if you specify which kind of lenses you wish to use, many of us can give you some detalided info about adapters, codes etc.
But... just a question... why a Visoflex
I ? Visoflex II/III are a lot more easy to use, operate, and also easier to find the right accessories. I think the only environment in which Viso I and Viso II/III are not too different in use with a Leica M body is macro photo with bellows... even if Viso II/III have a richer accessory set. With long tele lenses, Viso I is frankly terrible to use... almost impossible without a tripod or at least a monopod.