The admin dashboard templates that you see on ThemeForest are mainly just the front-end templates. They don't collect any data for you. If you were to build/code an application that will require some sort of admin pages, you would have to do 2 things majorly - 1) write the application logic to get all the data you want, and 2) show all the data in a neat form as a dashboard. The admin templates on ThemeForest mainly help you with the 2nd part - showing all the data you want in a neat form. So you can't really download those admin templates and configure them directly to show the data that you want, unless you link it to a backend that will actually fetch that data for you!
Hope that answers your question!