Get in touch with your schools AP exam coordinator (For me it is one of the assistant principals). They can give you some "big picture" information, and they set up the collegeboard exam and website permissions for the school.
You need a collegeboard account that will be apprved by the AP exam coordinator. The first stop when you have that account will be https://cbaccount.collegeboard.org/professional/dashboard where you will select AP/Pre-AP course Audit. "Course audit" is just college boards way of saying that you are the person teaching the course.
Within the course audit page, you should see the course you are teaching, or you may need to click the "Add Course" button. Once you add the course, you will need to wait for the AP coordinator to verify that you are the teacher of that course.
After the AP coordinator verifies the course, you will need to submit a course syllabus. The easiest thing to do is to use the pre-approved syllabus from a reputable online course. Both projectStem.org and code.org have these available to choose from. I recommend the projectStem.org course (See my endorsement below).
Once you are verified for a course and have submitted the syllabus, you will have access to the AP central website and AP classroom. Go to https://apcentral.collegeboard.org/ and log in. There are many links and exam information on this page. You can also log in to AP classroom from that page. This is the page to bookmark, because you will come back here often.
AP classroom has a ton of secure information. You will have classes that are enrolled by the AP coordinator based on your class roster. Students likely already have a collegeboard account from prior testing, but they often forget the login information. Their account should be based on their own personal email, not their fcps email. After the first week of school, I typically spend a good portion of one class making sure that all students can log in. This is also a good time to have them take one of the earlier released AP exams as a pre-test (You would need to set this up in AP classroom ahead of time).
*** it is important that all students enrolled in your class appear on your roster, and can successfully log in to AP Classroom. This will ensure that they are registered for the AP exam. (As of this writing in June of 2024. This is subject to change, so pay attention to AP examination instructions as they are announced during the Semester, or check with your AP coordinator).