How to create a new administrator account by restarting the Setup Assistant.
1.Boot into Single User Mode: Start/restart your Mac. As soon as you hear the startup tone, press and hold ⌘ + S until you see a black screen with white lettering. (If you end up back on the login screen after a flash of the black screen with white lettering, enter your password and it will return to the black screen.)
2. Mount the drive by typing /sbin/mount -uw / then ↩ enter.
3. Remove the Apple Setup Done file by typing rm /var/db/.AppleSetupDone then ↩ enter.