To start a group stream on Twitch, you first need to create a Twitch account. After you have created your account, you will need to visit the Twitch Settings page. On this page, you will need to select the "Streams" tab and then the "Create New Stream" button. After you have created your stream, you will need to select the "Group Stream" option from the "Channel Settings" tab. After you have created your group stream, you will need to select a name for your stream and then select a thumbnail for your stream. After you have created your stream, you will need to select a title for your stream and then select a description for your stream. Finally, you will need to select a game for your stream and then select a game mode for your stream.