This seems rudimentary but...

I'm attempting to analyze data in a pivot table.  I have three columns: the first being the main category and the second two being subcategories of the first.  The further columns to the right are costs.

I would like to analyze or group the subcategories to the main category.  When I bring the information into a pivot table, it populates one after the other, the subcategories at the bottom of the list of the column, not as subcategories of the main category.  It is a large data set, so I'm not sure that grouping would work and to process each, using the main category in the function field would be too arduous.  I do not have group as an option when I right-hand click.  Can you help? - I tried to post this once but am not seeing the original.  If this is a duplicate, I will remove it.