All StockCharts members have the ability to chart overlays of indicators. (This option is not available for non-members' charts.) If the “Advanced Options” area isn't visible, click the green triangle icon to make it appear. First, use the “Overlay” dropdown to select the overlay that you are interested in and modify any parameters if necessary. Afterwards, click the “Update” button.
To illustrate how this is done, here is an example of how to add a Simple Moving Average to the Price Indicator:
Here's what the finished chart should look like: