Hold volume up and power button until you see the RCA logo. Let go of the buttons after a couple seconds. An Android recovery screen will appear and you can select wipe data/factory reset. This will wipe the data.. If the factory image has a password pre-installed you will have to get this from the retailer who provisioned the unit.
The only way to remove the password from the factory image is to obtain it, then flash a different firmware without a password.