

To get it right now, you need to switch from release to beta which you can do with a click on Steam > Settings and on that screen enabling Steam Beta Update under Account > Beta participation. The feature launched in beta yesterday and it will take some time before it lands in the stable version of Steam. Steam Broadcasting is currently only supported through the Steam Client on Windows 7 and 8, but Mac and Linux support will be added later.The latest addition to Steam is the broadcast mode which enables users to stream and watch games using nothing but the Steam client. Thus if a tree falls in The Forest and there's no one there to watch, did it really happen? Right now the service only includes livestreams, so you can't save your footage. Players will be able to request that their friends watch them, too, should they be so inclined. The first time you get a viewing request you'll be presented with the broadcasting options. Steam users will be able to select who gets to watch their games, with options for anyone, friends only, only friends that you invite, or set it so friends can request to watch but you'll need to accept before they gain access.

To do this, simply go into your settings menu and change your "Beta Participation" to "Steam Beta Update." In order to give Steam Broadcasting a go you and your friends need to opt into the Steam Client Beta. When you see a friend is in a game - either from their profile or your Friends List - you'll see a button that says "watch game." Click it and voila! You can eavesdrop on their good time. Steam has introduced a new service called Steam Broadcasting that allows players to watch their friends play games with the click of a mouse.
