I work for the College Board in addition to teaching high school. Anyone can teach AP courses if you are qualified to teach the regular courses. If your school already has been accredited to have AP courses, you'll just need to submit your syllabus for the audit. Follow the link below to the College Board website for AP for info on the curriculum, the test, and submitting the syllabus for the audit. They have samples there.
If possible, try to get your school to pay for at least a weekend workshop, taught by College Board employees like myself who have taught the subject for a number of years. There you will get teaching ideas, materials, and advice on how to approach a new course offering. If possible, get to a weeklong seminar in the summer. Professional development credits are usually available.
On the AP website, there are links to English Literature and English Composition, whichever you are more interested in.