Right now you should only see your own user account when you select this tab. You can edit your account here. Your username will always stay the same, but you can change your name, email account and password here.
You can add users with this tab too. This is recommended if you have more than one person with site editing ability in your company. It is not recommended that you and/or your employees use the same login account. By each person having their own account, their account only needs to be deleted if that person leaves your employment.