The highlighted ticker on the left is what is displayed in the chart. You can change the ticker by clicking on another ticker in the list.
If you would like to change the set of tickers in the ticker list to a different data set, e.g. a different portfolio, watchlist or screener, or switch to the Quotes list or a to a list of stocks from an index, click on the pull down arrow to display the Navigation Panel and select the desired item you wish to display. The tickers listed will come from the new item you select.