If you add more columns within the source table, then refresh pivot
table, the new fields should appear in the list.
If the new fields don't appear, you can change the source range in the
Pivot Wizard:
1. On the PivotTable menu, choose PivotTable>Wizard.
2. Click 'Back' to go to step 2, and select the new range.
3. Click Finish, then refresh the pivot table.
Or, use a dynamic range for the pivot table source. There are some
instructions here: