In the subsequent window, open the ‘Format’ dropdown and choose ‘Mac OS Extended (Journaled).’.In Disk Utility’s left-hand menu, select your root drive.In the upper-left corner of the Disk Utility app, select the ‘View’ button and make sure ‘Show All Devices’ is selected.Open a new Finder window and navigate to ‘Applications > Utilities.’.Connect the external drive to your Mac.Once you have a suitable hard drive, the first step is preparing this drive as a GUID partition: In order to install macOS, you’ll need an external drive with at least 12GB of free space.
