To add a new stream, first of all ensure you are on the dashboard.
Once on the dashboard, use the "Search Twitter" button just above the columns.
Enter the phrase that you wish to search for. If you get stuck, use the help button on the right hand side (?) for assistance with different search terms. Once you have entered your phrase, click "Start as stream".
This will then drop your new stream on the right hand side over the "facebook feeds".