It is better to save the files on your computer than to open them online.

To modify the row or column breakdown criteria of an interactive table, please click in the table then on the "List of fields" button in the Excel menu "Pivot table tools / Options" to display the list of fields.

For more information on using interactive whiteboards, you can check out Microsoft's Office support videos Office support video sorting interactive whiteboard and Office support video creating interactive whiteboard (start at 2min19s).