You can compare other tickers to your primary ticker by entering new tickers directly into the ‘Compare To’ box, highlighted in the screenshot below.
In the screenshot below you can see chart with two tickers added to compare to the primary ticker. These tickers appear in the chart as two different colors.
You can edit the comparison tickers by selecting the pull down menu next to Compare to and here you can remove tickers and add additional tickers by typing the ticker directly ticker into Add box.
With multiple lines in the chart, if you mouse over the ticker at the top of the chart it will bold the line so you can better see the line in the chart as highlighted in the screenshot below.