It's actually called the California Public Records Act. While it has a different name and is the state level version of FOIA, it does essentially the same thing.
Some agencies have a form they can have you fill out to request records, but in most cases you have to write a letter requesting by description what records you want access to. While it doesnt cost anything to look, you may have to pay for copies or duplication.
They have a certain time limit to respond and the law keeps them accountable if they dont respond. Some records can be withheld if there is a compelling reason; such as the identity of minors as victims- but more pertinent to our uses, the records we seek might be protected if it is the subject of an ongoing investigation. This is why we should compel the authorities to share their records before filing a complaint. Because once you file a complaint, its possible that the records you seek will be withheld on the basis that an internal investigation prohibits their release.