HOW TO Use Time Machine in macOS Recovery
Recovery mode
On an Apple silicon Mac, shut down, then press and hold the Power button. Click Options from the startup options, then Continue. On an Intel Mac, boot while holding Cmd+R and release when you see the Apple logo.
Restore from a backup
In the macOS Utilities window, choose “Restore from Time Machine” to recover all the files and settings from a recent backup. Follow the instructions on screen to choose a backup.
Restore macOS
To reinstall macOS, choose that option from macOS Utilities. Follow the on–screen instructions. When Migration Assistant launches, choose “From a Time Machine backup or Startup disk”, click Continue and choose the backup.