You don't access any files on the MC via the PC to install. The only thing you use the PC for is to copy the FMCB installer to a USB stick. (also the required files to boot the installer if needed by the tutorial)
FMCB is installed directly to your MC on your PS2.
And as mentioned in the tutorial, you need either an Action Replay Max, Codebreaker (8.1 or newer), or Swapmagic. But those are too be used to boot the installer.
If you need help, post a question in the
forums, not my PM inbox. Thank you.