How can I modify the font and size of my ATC button?

[Liquid_xPert_SJ]

Hi @michaelhopper17 welcome to the Shopify Community,

Please add the below code to your theme customizer and adjust the font size according to your requirement.

product-form .quick-add__submit span, product-form .product-form__submit span {
    font-size: 22px !important;
}

Theme Customizer:


Results:

Thanks