If you're streaming to a common service like Twitch or YouTube, just select it from the dropdown list in Settings -> Stream.
Also, sounds like you should check out the new user guides here:
If you're new to OBS Studio, the community has created some resources for you to use. Check out our Quickstart Guide at
http://goo.gl/bLzO5T and Nerd or Die's video guide at
http://goo.gl/dGcPZ3