To follow a piece of content, click Actions in the top right corner, then select following"
Stop Following People, Places, or a Piece of Content
To stop following something, either hover over it from the stream or go to the item and then click Following. Select the streams from which you want to stop following the person, place, or content item, and then click Stop Following. You will no longer see updates for that person, place, or content item in those streams. Those updates will still appear in the Activity stream, however, because that stream shows all public activity in the community.
You can also click the gear icon next to the stream and click Edit stream to use the stream drag-and-drop feature.