Help about insurance in buying a used cars!

hi guys,



i live in California and i want to ask what do i need to do with auto insurance so when i buy the car i will be able to drive it home on the same day.is it right that i need to register the auto insurance first before buying the car then when i buy the car i just need to call the insurance company and give them the VIN of the car?is it possible?



Thank you



Regards,

Andrew