You can order a personalized license plate on the website of the Department of Motor Vehicles of your state. As of September 2015, the fee for a personalized license plate is $98 in California and $10 in Virginia.
To get a personalized license plate in California, navigate to DMV.CA.gov and select the Plates option in the Vehicle Registration menu. Then, click on the Order Special Interest and Personalized Plates Online option. You can choose a background and create the plate number for your personalized license plate. When you receive a postcard to pick up the personalized plate, make an appointment with the DMV to pick it up.