Most first-time driver’s license applicants must take and pass a Knowledge Exam consisting of a Road Signs and Road Rules test.  All information you need to pass this test can be found in the Driver’s Handbook. 

There are many sites that have practice tests. Each of them has questions that are similar to the questions you will find on the actual test.  Visit more than one of them to get lots of practice.

Driver's Handbook Driver's Handbook 2 tests with 8 questions each
dmv-written-test.com practicetest.aspx 15 tests with about multiple sections each
driving-tests.org california-permit-practice-test multiple tests with about 40 questions
drivers-license-test-online.com california-ca-dmv-practice-test 11 tests with a total of over 400 questions
https://quizlet.com california-drivers-permit-practice-test-flash-cards/ About 70 questions