Hello,
In this case, it would be better to use custom CSS code. Please select http://prntscr.com/qacuv5 in settings of the wishlist and add the next code in Theme Options > Theme Custom CSS:
.single-product .product-content .yith-wcwl-add-to-wishlist a {
border: 1px solid #222;
padding: 7px 15px 5px;
}
you will get – http://prntscr.com/qacx2e If you are looking for something else, describe the desired result in more detail and we will help with the custom CSS code.
Regards