If you want to fly any RC aircraft (over 0.55 lbs – 250 grams) in the National Airspace, you will need to register with the FAA. Info on registration is located here – https://faadronezone.faa.gov/#/

The AMA website has a nice summary of the Know Before You Fly information, located here – http://www.modelaircraft.org/aboutama/govkbyf.aspx