I just finished my freshman year of high school and am looking to get ahead. How do they work exactly? Is it an online thing, or? Can someone run me through how I would go about signing up for these? Sorry for all the questions, the educational director at my school told me flat out there was “no such thing.”
I don’t have personal experience with this yet, but from what I’ve heard, you can self-study for AP exams. Sometimes students take a non-AP course and then take the AP exam on that subject. (For example, taking Honors Biology and then self-studying for the AP Bio test.) You can use prep books, online courses, videos, etc. to study for them.
As for the actual test, you’d probably have to check if your school or a local school offers it and sign up at that location. I don’t know too much else, but there definitely is such a thing as self-studying APs.
Here’s a good thread (a bit outdated, though) that is still relatively active: http://talk.collegeconfidential.com/ap-tests-preparation/369861-self-studying-aps-improving-your-app.html
If you self-study an AP course, all you need to do is study the material on your own. Download the textbooks for your selected AP course either on the internet or borrow the textbook from your school. Go research on the internet for practice tests and buy prep books like Barron’s and review the material. When your school asks you to go sign up for AP testing, just pay for the one you’re planning to take. Basically, self-studying an AP class is on your own accord and it’s going to be at your own pace so plan accordingly to your own abilities! I’m taking 5 AP classes next year and self-studying AP Psychology and maybe AP Art History! 
I’m assuming you want to self-study an AP class your school doesn’t offer. If your school offers the class, you should take it.
Tell your guidance counselor you want to take an AP exam for a class your school doesn’t offer. Someone at your school will order a single test for you, and someone will administer it in May. I self-studied four AP exams in 2013, and that was how it worked for me. :-/
If your school doesn’t understand this, see if you can find another local school that offers the AP exam you want to take. Find out if you can take the AP exam with their students. The College Board website describes this [url=<a href=“https://apstudent.collegeboard.org/takingtheexam/registering-for-exams%5Dhere%5B/url”>https://apstudent.collegeboard.org/takingtheexam/registering-for-exams]here[/url].