User accounts can only be managed by administrators. If your currently logged in account has administrator privileges, then you can see a Users table in the settings page.
There you can add new users by clicking the add button.
To manage an existing user, just search them in the table and click on them. You can reset their password, promote them to an admin or demote them or deactive their account completely.
Deleting an account is not possible yet. Deactivated accounts just are unable to log in, their data still exists. They can be reactivated at any time.