Ecamm Live does not allow you to live stream to Instagram. Instagram has a closed API and does not allow any apps like ours (or others) to broadcast there. Currently, the best way to live stream to Instagram is using your phone and going directly through their app.
If you really want to use Ecamm Live to broadcast to Instagram, there are a few workarounds/hacks, including Loola TV, Yellow Duck, and Instafeed.
If you really want to go out to Instagram, the above apps will work to take you there, but they can be less stable and reliable. Use with caution.