The next screen will display all of your backups.

On the ‘Restore from Time Machine’ screen, click ‘Continue.’.

In macOS Utilities, select ‘Restore from Time Machine Backup.’.

Release these keys as soon as you see the Apple logo.

Restart your Mac while holding down the ‘Command+R’ keys.

If the backup is stored on an external or network drive, then make sure this drive is available to your Mac.

Reinstalling an earlier backup will undo all the changes you made since creating this backup, so make sure all of your documents and data are stored somewhere safe before proceeding. If you create regular Time Machine backups (and you should!) then you may be able to reverse a macOS update by restoring a Time Machine backup that you created before installing that update.

Choose your startup disk, and then select ‘Install.’.

Once you see the macOS Utilities screen, select ‘Reinstall macOS’ and then click ‘Continue.’.

Restart your Mac, while holding down the ‘Shift+Option+Command+R’ keys.How To Properly Factory Reset a Mac & Reinstall Mac OS

How to update your mac software 10.13