How to add (new) Categories in Numbers?

First time user to Numbers (app for OSX) Am trying to create a very basic table of personal/business expenses for tax purposes. I have no experience using accounting/spreadsheet software.

I started with the Personal Budget Template. this is not for "Budgeting" I only need to list/compile Expenses, and am only using Transactions. I need only 3 columns (headers?) Description/Category/Amount

• I can't add new Category names under Category. There are only options for "Auto, Entertainment, Food, Other, etc" And I unchecked "freeze header Rows/Columns".

When I try to entire new Categories, I'm not permitted to input text.

• Perhaps there is a better template to use for this, Seems like "Personal Expenses" is closest to my needs. I don't have time for much of a learning curve.

thanks