Follow the instructions here.
(Additionally, I got Eclipse all set up to create Android apps as well by following the steps here. That may be some extra steps to take if you are having trouble)
I ran into a couple snags. If you get “adb: command not found” when trying to run adb in Terminal or trying to run an Android app in Eclipse, that means you have to add your android SDK path to your system path. Follow the incredibly patient instructions by bftb0 in post #9 on this thread.
Afterwards, adb should be able to detect your Kindle Fire. Good stuff.
But now, you launch Flash Builder, set up a new Debug Configuration with Google Android, launch on device, Select Debug with USB, and Flash Builder doesn’t see your Kindle Fire!
No worries, just restart your computer. That did it for me.