Installing Double winder stair

[dooza]

Hi everyone,
I am in the process of replacing a straight flight staircase into my loft for a double winder stair (I manage to gain a lot more space to the bedroom this way). The stair is to arrive in 3 pieces - the 2 winders (with newel posts) and the straight flight.
Does anyone know what is the best method of joining the 3 stair parts and also how to install it? The stair will be installed against an existing external wall and I'm not sure whether you bolt the stair to the wall through the underside of the string or what to do with the winders!
Any help greatly appreciated!

Thanks,

dooza

 

[chappers]

it should all be quite obvious when the staircase arrives as any good joiner will have put it together first. A few decent screws and pugs through the underside of the string will suffice they don't take any weight just hold it to the wall so to speak.
The technical bit is sortiung out the arrangement of your supporting floor joists