If you can't see this button, click Erase instead.
Format: APFS or Mac OS Extended (Journaled), as recommended by Disk Utility.Click the Erase button in the toolbar, then enter the requested details:.Select Macintosh HD in the sidebar of Disk Utility.From the utilities window, select Disk Utility and click Continue.If asked, select a user you know the password for and enter their administrator password.