The Admin view allows you to manage users, to add them, make them administrators, delete them, or change their passwords.
To make a change in a current user's password, click edit, in red above. To add an additional user, click +Add Local User. In both cases, a variant of the username pop up appears.
For a new user, enter the desired Username and Password. Check Admin to make this user an administrator. For an existing user, enter the old and new Passwords. Make your changes and click Save.
