"Beginning with Lua" won't teach you to program. You must learn that somewhere else.
Once you know programming theory, "beginning with Lua" will get you on the right path.
This is the best advice and help I can give.
Don't get fooled by the name "script".
Lua scripts in Orbiter are full programs, with user input,conditions, loops, etc, etc.
All very basic stuff, but they do require a minimum of theoretical knowledge.