If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.If the installer asks to unlock your disk, enter the password you use to log in to your Mac.Select Reinstall macOS from the utilities window in macOS Recovery, then click Continue and follow the onscreen instructions.įollow these guidelines during installation: