How can I play games on school computer

I’ve seen a kid play mortal combat and crash bandicoot with something called PCSX, I think. I’m wondering how I could download them and then also find games to play.

Or if there’s any alternatives, like how kids at school used to download things from SteamRip and then use another app to extract files from a zip folder or something. So I’d liked to be informed on how to use PCSX or any other tools there could be