I am trying to understand how much money I spent by category during the month or year. Where can I see that information?

On the Annual Overview tab, you can scroll down to see monthly totals by category for Income, Savings, Debt, Needs and Wants.  At the far left, you will see a yearly total (for the months you've tracked) as well as a monthly average.  Be aware that the monthly average calculates an average for all months with data.  So even if you only tracked one purchase for a month, all categories will be averaged for that additional month as well.