Many of the people working at Area 51 and the NTTR are civilian contractors, employed by a parent company called JT4 (for Test, Tactics, Training, Technology). On their web site under the "Careers" tab you can find current job openings.
Of course there is also a large presence of USAF personnel. But in the Air Force you don't apply for a job at Area 51. In fact that would probably be an immediate disqualification. Instead, outstanding airmen who excel in their field are selected to work there.