On the bottom left, look for Users & Groups. Select the padlock symbol. Enter your password On the left side, choose an admin user, and then hit the minus sign next to it. Choose a choice from the drop-down list and then Delete User.
You may quickly regain admin access by restarting Apple’s Setup Assistant tool. This will run before any accounts have been loaded and will operate in “root” mode, allowing you to create new ones on your Mac. Then, using the newly created administrator account, you can restore your admin privileges.
Turn off your Mac and then start it up again immediately holding these four keys together: Option, Command, P, and R. After about 20 seconds, release the keys. This erases user preferences from memory and reinstalls security features that may have been disabled as a result of changes.
Open Sharing preferences for me, then click Locks. Unlock the preference pane by clicking the lock at the bottom left corner. In the Computer Name field, type a new name.
Select the Users & Groups option from the Apple menu, then click Users & Groups in System Preferences. If the bottom left lock is unlocked, click it to open the preference pane. In the list of users, choose a standard user or a managed user, then choose “Allow this computer to be administered by this user.
