Emulation is a new project for me on Apple Devices and I really like the RetroArch system. I was able to keep track of my game saves and open all games, except playstation. With the help of google I was able to find the appropriate bios files, but I didn’t know where to put them.
If you are searching, hopefully this will help you.
As of version 1.5.0 you will navigate inside RetroArch to: settings > directory > system/BIOS
now you will navigate your file system to locate the files you want to use. I navigated to the folder holding the appropriate 4 files and now my Playstation games work.
I hope this saves you the time it took me to find the answer!