Click on the field's drop down menu, in either of these locations:
Through the Columns/Rows list
Through the Table Preview
Select the Total option from the list and click on the aggregation you wish to use for the summary.
You should now have a total on your field.
Expand
title
Column Formatting menu
v
Click on the Column Formatting menu in the main navigation bar of the page Image Modified
Select the field you wish to apply a total to in the Report Fields list panel on the left of the menu
Open the Summary section of the menu to view the available options
Define the Total Aggregation option. Image Modified You will notice that using the Column Formatting menu rather than the Field Drop Down list means that you have a range of additional options, rather than just the ability to select the aggregation to use. These will be explored below.
You should now have a total on your field. Image Modified