Don’t change your username

QHow can I change the main and only username and password on my Mac?

AChanging the password is simple: open the Users & Groups pane, select the user, select the Password tab, and click on Change Password…

Changing the username isn’t wise, as it’s used to create the name of the Home folder. That short username also appears in many other places, most of which you can’t edit, so they’d stop working. Advanced users can change the Users listing with the Directory Editor in Directory Utility, but you must know what you’re doing there or you could make your Mac unusable and lose access to your Home folder.

If you really want a different username and password, it’s far safer to create another account in the Users & Groups pane, and leave the first user alone.

You can change your login password in complete safety using the button provided in the Users & Groups pane. Only confident advanced users should change user settings in the Directory Utility, or you could lose you entire Home folder.