When you're ready to reinstall macOS, choose Reinstall macOS from the Utilities window. Then click Continue and follow the onscreen instructions. You will be asked to choose a disk on which to install.

If the installer asks to unlock your disk, enter the password you use to log in to your Mac.

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 is for a different version of macOS than you expected, learn about macOS Recovery exceptions.

If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.

Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.

If your Mac restarts to a setup assistant, but you're selling, trading in, or giving away your Mac, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.