What you are linking to is not a sample app, it is a widget.
It is a building block for an app, but you first need to create an app and then you can download the widget into it.
After downloading, you need to include it somewhere in your app and set up its configuration.
The widget you link to, by the way, is considered deprecated (as you can see in both the Description and the Documentation parts for it when clicking the link). So I wouldn’t use it. The description recommends ChartJS instead.
Edit: The documentation for ChartJS recommends ‘Charts: see https://appstore.home.mendix.com/link/app/105695/ ‘ (quote from the description for ChartJS)