If you want to boot a physical computer:

In the VM settings, mount your in the virtual optical drive. Start the VM and follow the on-screen installation prompts. Method B: Physical Retro Hardware If you are building a "Period Correct" PC:

His father’s machine, a beige tower with a turbo button that did absolutely nothing, had just suffered a catastrophic hard drive crash. The screen displayed the dreaded “Invalid system disk” message, blinking like a hospital monitor flatlining. Leo’s father, a man who balanced checkbooks with a fountain pen, threw up his hands. “Call the repair shop.”

Most retro enthusiasts don’t use an ISO at all. They use WinImage or Rufus to write the raw .img floppy files to real floppy disks using a USB floppy drive. That’s the authentic experience. Alternatively, for emulators like DOSBox or 86Box, you don’t need an ISO—you just point the emulator at the .img files directly.

Microsoft no longer sells or officially supports MS-DOS. However, because it is considered "abandonware," several reputable community archives host the original setup disks and pre-made ISO images. 1. WinWorldPC

Hosts community-created MS-DOS 6.22 bootable ISOs that combine the floppy images into a single CD format.