1.- Go schedule your DL-51 physical exam with your physician and have them complete the entire form.
2.- Look up your particular county's certification requirements (all basically the same; it does not matter which county you get certified in unless the county you wish to work in has additional scope of practice requirements).
3.- Get your LiveScans done for the DMV and for the county ($$).
4.- Go buy a CA Ambulance Driver's Handbook (hardcopy only) from the DMV, flip through it, and get your *cant post links*
5.- Get certified by your county.
6.- Start applying for jobs.
In the meantime, while you're waiting between each of those steps, go take online cert classes (which will likely be required sooner or later anyway) for AWR 160, ICS 100, ICS 200, NIMS 700, ICS 3, ...
It's a long process, but stick with it. Best of luck!