OS X Mavericks: If you’re asked for an administrator name and password
To complete certain tasks, you must enter the name and password of an administrator to verify, or “authenticate,” that you are a user with administrator privileges. If you’re in a secure environment where smart cards are required, you must insert your card and enter a personal identification number (PIN) instead of a password. You should always be sure you know which app is requesting this information.
If you don’t know an administrator name and password, ask the person who administers your Mac for help.
The user you created when you set up the Mac is an administrator. You can also add additional administrators on the Mac. If you set up the original user but don’t remember the password, see: