Click in the search field in the upper-left corner and type the ticker symbol. Press "Enter" to add the ticker to your watchlist.
Another window will open up with a complete list of all of the column headers to choose from.
Click the box adjacent to the column header name. A blue box designates that the column header is active within the watchlist. A white box designates that the column header has been removed from the watchlist.
(See the two images to the right).