https://www.dmv.ca.gov/portal/dmv/?1dmy&urile=wcm:path:/dmv_content_en/dmv/dl/dl_info#two500
How to apply for a driver license if you are over 18
If you are a visitor in California over 18 and have a valid driver license from your home state or country, you may drive in this state without getting a California driver license as long as your home state license remains valid.
If you become a California resident, you must get a California driver license within 10 days. Residency is established by voting in a California election, paying resident tuition, filing for a homeowner's property tax exemption, or any other privilege or benefit not ordinarily extended to nonresidents.
To apply for an original driver license if you are over 18, you will need to do the following:
Make an appointment before visiting a DMV office (walk-ins are only accepted at our Driver License Processing Centers).
Complete application form DL 44 (An original DL 44 form must be submitted. Copies will not be accepted.)
Give a thumb print
Have your picture taken
Provide your social security number. It will be verified with the Social Security Administration while you are in the office.
Verify your birth date and legal presence If your current name no longer matches the name on your birth data/legal presence document, see "True Full Name" and "How to Change Your Name" for more information.
Provide your true full name
Pay the application fee
Pass a vision exam
Pass a traffic laws and sign test. There are 36 questions on the test. You have three chances to pass.(Sample Test)