Enroll in a credential program, either at a state university, private college, or college for adults (Chapman, National, JFK, etc.). It really doesn’t matter to the district that hires you.

You might even be able to get a paying job while you are taking your coursework (36 units) through one of these institutions. Be aware of accelerated programs like Project Pipeline, which offer little support.

The biggest cautionary advice I have is not to mistake knowing chemistry with being able to teach chemistry to high school students. If you can at all afford a program that offers a student teaching opportunity, or can afford not to have a full-time salary during that semester, then spend the time in a situation where it is understood that you are still learning. You will be able to make a novice’s mistakes in a supportive atmosphere.

good luck!