Adding categories to the legend?

[BlackMagic21]

I'm sure there is a simple way to do this, and I just can't figure it out for some reason. How do I enter in the categories for my legend? Right now I've figured out how to do the pie chart but it list everything under 1, 2, 3, 4 and so on. How do I change the 1, 2, 3, and 4 to titles of my own choosing?

[Andy Pope]

Right click > Source Data.
Series tab select the range for Category Labels.

[BlackMagic21]

Thank you!