Whatever site you want to stream to should give you a URL/server address and also a stream key or token the latter of which is unique to you. Any site I've streamed to usually releases this info to you once you chose the external encoder option ie OBS, ManyCam instead of a flash browser based encoding.
Watch out for Streamate, they want you to use a fresh key every session which is a pain in the ass. I just use their own encoder. They're very proud of it!!
