Reply To: add to cart button customization

Hello,

Please try this code to the Theme Settings > Custom CSS:

.single_add_to_cart_button{
    background-image: url(http://dummy.xtemos.com/woodmart/wp-content/uploads/2017/06/newsletter-new.jpg?id=220) !important;
    background-repeat: no-repeat !important;
}

Replace the URL with yours one.

Best Regards