We'll be making changes and fixing bugs during the beta period, so please add your feedback to the discussions!
To try out Broadcasting now, both you and your friends need to opt into the Steam Client Beta. In the Steam client main menu, select Settings > Account and change your "Beta Participation" to "Steam Beta Update".
You can now watch and broadcast VR games on Steam using Steam Broadcasting. To start a broadcast, invite a friend to watch from the Dashboard, or accept a friend's incoming request by pressing the System button when you receive the notification.