It's easy. You install the emu, you start Snoopium and try to run an OS4 program and then see which files are missing. You can get them from Aminet or os4depot. For shell tools you do not need much more, maybe some libraries. For GUI tools you need ClassAct/Reaction which is mentioned in the readme. You can download ClassAct from Aminet but it is older than the current Reaction on OS4. But in the end don't expect many programs will run because this is not a complete emu. And I think it is not needed anymore these days because for most programs we have good MOS programs anyway.