Option 1: Hover over the field in the workbook’s field picker and select the three-dot menu that appears and then select Aggregates in the menu. Or right-click on the field in the field picker to see the same menu.
Option 2: If the field is included in the results tab, hover over the column header in and select the vertical three-dot menu that appears in the top-right of the column or right-click on the column header and then select Aggregates from the field’s menu options.