Depends where you want to teach (which state), but look up what is required by state for a teaching credential, usually it is an extra so many classes. In Ca I would look at the ca sept of education website for information, it depends again on what state you are in. You might also have to take some tests. Some schools will hire while you are working on a credential, some won’t. Usually there are programs during the evening, like univ of laverne or point loma univ (again in Ca) where you can get your credential in a year or so, they are geared towards individuals working/teaching while getting their credential.