Hi Andini,
You can create an NPE. and use a dataview of the NPE as the parent of the datagrid, once you click on the import button, you can use a change object activity, and refresh the NPE on the page, to reload it on the page.
THis will re-render the datagrid, and will start showing you the new data.
Let me know if you have any issues,
Hope it helps!