The FAA registration is a requirement for all people flying model aircraft. According with the FAA guidelines, members need to list both the AMA number and the Federal registration number on their aircraft, at least until a new registration process is finalized with the FAA.
For FAA registration, the official website is at: https://registermyuas.faa.gov/
Questions and Answers on the UAS registration can be found on the FAA website, at: https://www.faa.gov/uas/registration/faqs/
The AMA position on the registration process is summarized at: http://amablog.modelaircraft.org/amagov/2016/01/11/update-uas-registration-frequently-asked-questions/
Also read the AMA message released on July 21, 2016, about the latest FAA position on aero modeling, by clicking here.