Besides presenting the history of stage changes under the Stage Tracking tab of the Opportunity, the most important feature of this add-on is its ability to alert you when an opportunity is staying too long in one of its stages.
To set up this feature, launch the add-on (either by clicking the icon on the Opportunity List view toolbar, the icon at the right of the toolbar under the Stage Tracking tab or by using the Tools > Opportunity Sales Tracking menu and click the Define & Manage Alerts button to open the following window.
In this window, you can set up alert levels for each of your stages. To set up the levels, select one or more stages and click the Edit... button.
If you set one of your stages like in the above window, it means that an opportunity at that stage will be shown in green between 0 and 14 days, in yellow (orange) between 15 and 29 days and in red above 30 days.