i'm interested in becoming an insurance agent/broker for commercial vehicles. How do i get started?

You go to the California Department of Insurance website, and look for Producer Licensing. That will explain what you have to do to get the license.

THEN you have to find an insurance company willing to let you sell their insurance. Good luck. They don't appoint "green" agents with no experience. The best way to get experience is to get hired as a CSR at an agency.