Great guide from Bijan Stephen at The Verge that runs through the basics of streaming:
I keep writing about live-streaming like it’s accessible and easy to do — which it’s not. It’s actually quite difficult to get started. Sorry! My bad. I didn’t mean to lead you astray. If you’re still Twitch-curious, I have a gift for you: a guide for how to get started.
This is a nice complement to the piece I wrote last month about streaming Jackbox games via YouTube; it goes into more details about tools like OBS and hardware options. Highly recommended if you’re interested in streaming.