If you live in an area that doesn't offer the AMCs, you can arrange to make it happen locally. You will need to work with a local school, church, or library. Parents can't proctor the AMC if their own children are taking the exam, and the exams will be delivered directly to the contact person you have designated.
You order exams in bundles of 10, so try to recruit friends to participate too. You can't register individually with the MAA directly. They aren't set up to handle that. You need to contact sites locally or organize your own (in conjunction with some official group as described above.)
2017 AMC 8 Registration Form For students in grade 8 or younger
2018 AMC 10/12 Registration Form For students in grades 10 or 12 or younger
And don't worry, the "early bird" deadline isn't until October for AMC 8 and January for AMC 10/12. Just posting in case you need extra time to make arrangements.
Edited by daijobu, 12 May 2017 - 12:52 PM.