The demo for the control is in the link provided. Using it in Sitefinity is the same way you use any other control. I have recorded this short video
of a custom widget with the PaneBar control within. To populate the control with real data please refer to the control's documentation for the specifics. In Sitefinity side you can use the API to gather the information to populate in the control, for instance.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items