Developing BAR Lua with the ZeroBrane Studio IDE - beyond-all-reason/Beyond-All-Reason GitHub Wiki
So you have decided to check out the repository, to have a look at what is present inside of it.
You may use any other IDE (dont use notepad++, notepad++ is not an IDE) you wish, like Visual Studio Code, and install a Lua Language Server extension for it, but that is not covered here.
Installation steps:
Download and install Zerobrane Studio, this will be referred to as ZB.
From https://studio.zerobrane.com/