Brand New Macbook Asking for Password

If you had paid attention during the setup you would have started by creating an admin user account and asked to enter a username and a password. That's the password the computer wants you to enter. If you aren't able to make progress or get to Security & Privacy preferences, then see the following:

Forgot Your Account Password

Boot to the Recovery HD:

Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

When the menubar appears select Terminal from the Utilities menu.

Enter resetpassword at the prompt and press RETURN. Follow

instructions in the dialog window that will appear.

Or see:

Reset a Mac OS X 10.7 Lion Password

OS X Mountain Lion- Reset a login password,

OS X Mavericks- Solve password problems,

OS X Lion- Apple ID can be used to reset your user account password.

Indeed you are. Did you try booting from the Recovery HD? If you need to shut down the computer just press and hold down the Power button until it shuts off. Wait about 30 seconds before you restart.