You won't be able to stream gameplay from your Xbox One at launch this week. In fact, you're going to have to wait until next year for those features Microsoft have revealed.
"We know the ability to instantly broadcast gameplay is something the gaming community is excited about, and we are too. We are working to ensure the initial Twitch on Xbox One broadcasting experience meets the expectations of the Twitch community, so while this feature won't be available right away, we'll let you know as soon as it is ready. Our goal is to deliver it during the first part of 2014."
In the meantime you will be able to use the Twitch.tv app to watch PS4 gameplay and earn "media achievements" we suppose...