Unscrew the eyepiece before adjusting elevation, screw it down tight after.
Windage adjusts as-is.
Choose the eyepiece aperture that provides you with the best picture of the front sight.
Telling you how much it raises per revolution is time wasted, as the elevation or windage depends upon the distance between the sights.
Not much else to know.
Hit http://www.rifleman.org.uk/BSA_sights_and_accessories.htm and check out what they have to say about it.
Like as not, that is going to be as close as anyone will ever get to a 'manual'. These are a product of a time when you were expected to understand some basics about things.
Like as not, that one is shaped to match the rear hump of a small BSA Martini action, but they were offered up as aftermarket spares for fitting where the buyer saw it as useful.
