Can I use the Japan Rail Pass from the airport?
Yes. The JR Pass is valid on the JR lines that connects the main airports to the main cities.
If you land in Narita Airport, you can take the Narita Express to connect to Tokyo, Shinagawa, Shinjuku and Ikebukuro stations. If you land in Haneda Airport, you can catch the Tokyo Monorail, which connects the airport to Hamamatsucho station. And finally the Limited Express Haruka that connects Kansai International Airport to Osaka or Kyoto.
However, if you land at Fukuoka airport or Nagoya you will have to reach the JR Hakata Station to exchange your Japan Rail Pass, and from Chubu Airport, you will need to take the Meitetsu train to Nagoya Station.
To start using your JR Pass you will need to exchange it. Read more about it here: "Where to activate my Japan Rail Pass?".