Go to your main file explorer, program files x86, steam, steamapps, common, railworks, manuals. Hope that helps. God bless.
A forum search for manuals should have lead you to this thread... (Unfortunately it now also leads to this thread and loads of others like it! )
Wrong forum, this is Train Simulator not Train Sim World. https://forums.dovetailgames.com/forums/ps4.138/ That's the forum you want