Propeller-turbine characteristics

Hello all,

I am a noobie regarding naval architecture and would like some help.

Reading a book about naval architect, I found this diagram here:

But I have no idea how to interpret it.

Where do I have to start? Is it with the “free astern shp in % ahead shp” for the vessel concerned and after this choose the astern RPM? But with these steps I am totally forgetting the propeller characteristics curves. How do both correlate with each other?

Well, any help will be good.

Kind regards