This thread could help you: you ll find some docs and tutorials
https://www.orbiter-forum.com/showthread.php?t=39604
But before going there I think it is important to understand how the real shuttle was operated since SSU aims to replicate that. You will not be able to maneuver the ship, fire the engines or operate systems by pressing a single button or flipping a switch like you do with most of the vessels, you will need to follow specific steps and procedures to make that happen.
So, until a full detailed user manual is published, I am afraid you will have to open and read some NASA Shuttle manuals