With the growing positive feedback of PSXmit, most people don't know that the original PSXmit won't be updated anymore, and it's being replaced with a better version, that uses a single sprite for the entire BIOS. In this project, there's a simple explanation in how to install any BIOS into the project (This also works with games.)
PSXmit BIOSes: https://scratch.mit.edu/projects/617609058/editor/ PSXmit 1sBIOS Simulator: https://scratch.mit.edu/projects/616708290/editor/