using aenet for ANN potentials in this case for elucidate non-stoichiometric FeS structure
this research basically use all the resources and tutorial from http://ann.atomistic.net/ as the main reference
in this github page you'll see 3 branches which indicates the three steps to get where you needed to, and since the author still on his own study the research might be a little bit off but I wish it's not that far off.
You'll notice each branch has its own readme as well to guide you through what you needed to do on each section.
But first thing first, you need to install aenet itself to your own machine which you can see on http://ann.atomistic.net/documentation/
Best of luck!