Use the commands from this post to get a new FA id:
https://discussions.flightaware.com/t/problem-with-new-install-of-my-old-site/44727/2?u=wiedehopf
If you’re looking for graphs or an additional webinterface, have a look here 
https://github.com/wiedehopf/adsb-wiki/wiki/Raspbian-Lite:-ADS-B-receiver