Once you become 18, you are a legal adult (unless under a conservatorship). Visit the California Department of Motor Vehicles and obtain information on how to acquire your own CA Photo I.D. or CA Drivers License if so qualified. These are essential tools in life.
If you are a man ages 18 through 25 and living in the U.S., then you must register with Selective Service. It’s the law. According to law, a man must register with Selective Service within 30 days of his 18th birthday.