I was interested in taking AP Seminar and AP Research, but they’re not offered at my school. Is there any other way I could take them? Thanks.
@tspmf12 No, they are only offered at select schools. At this point of time, they do not offer it online
The AP Capstone program is not exactly something you can self-study for. 
Your school needs to be authorized at the moment, but I’m sure that they’ll come up with a better system in only a few years. (unfortunately, you and I would both be in College by then)