How to add a product option on my payment form?

in payment settings, I'm offering "shorts" to purchase; however, adding a "product  option," I want to ask for "size," but your preset only offers "t-shirt size."

Is there a way to modify that?

You can edit the label of the product option to size and add the sizes you want.

Then save the option.

Here is a sample screen cast:

Please give it a try and let us know how it goes.

Thank you.