Drag & Drop fields into the Grouping/Dimensions area that you want to segment by (This will auto-add the field into the Fields/Metrics area).
Add the field to aggregate into the Fields/Metrics section.
From the pop-up, select the aggregate option.
Add any optional filters as needed.
Optionally, change the widget type/settings to modify the visualization settings.
Add limit by entering the number of rows to be returned by the query after any sort of criteria has been performed. Leave blank to bring back all rows.