Yes, if anything that you fly is over ~1/2lb, you have to be registered. On the FAA link I noted above, read Step 1, which contains a link in the text to start the registration process.

In the FAA’s eyes, any remotely piloted vehicle is a “drone”. And in those pages, they seem to think a person would only have one, so it implies you have to register each - but deeper in the process, you find that you only need to register once for all your aircraft. The AMA has been trying to get them to accept the AMA number as a valid registration number, but no firm result yet. So at this time you need to have both on your plane. Several of my fellow club members protest this by printing very small stickers with micro-print, and putting the FAA number in the hinge line of their plane!