How to add columns on a Numbers chart

To get a feel for how charts work have you -

-- looked at the 'Charting Basics' template at File > New in your menu?

-- had a look at the entries on charts in the User Manual?

Modify chart data in Numbers on Mac – Apple Support (UK)

Select data to make a chart in Numbers on Mac – Apple Support (UK)

And many more. (If you are on a Mac you can also access the User Guide via Help > Numbers Help in the menu.)

SG