If you want to start up again from the disk you erased, select Reinstall macOS in the utilities window, then click Continue and follow the onscreen instructions to reinstall macOS. Erase and reformat a storage device in Disk Utility on Mac If you want to erase your startup disk: Start up from macOS Recovery, then choose Disk Utility from.
If you don't see this button, click Erase instead. Either head to Applications > Utilities, or tap Command + Space. Step 1: Connect the USB drive or external drive to Mac and launch the Disk Utility from Applications.
