I am not sure exactly what you are asking but, you can play .flv files via netstream and netconnection.
var nc:NetConnection = new NetConnection();
var ns:NetStream = new NetStream(nc);
You are probably better off using a .swf to play an externally located .flv, unless you video is less than ten seconds. If it is short you can simply embed it in the timeline. To convert your video to flv you can use many different apps. I personally use quicktime pro. Good luck