1) If you want to use the button instead of simple text + icon go to Wishlist > Colors > http://prntscr.com/mui059 edit the options according to your needs: enable icon, change the bg color, add the border. Add the following styles to child theme style.css to remove our default wishlist icon
2) Image in the plugin description is wrong because if you check their demo https://plugins.yithemes.com/yith-woocommerce-wishlist/product/yith-bag-roger/ you’ll see that add to wishlist button is located below the Add to cart button and even out of the Add to cart block http://prntscr.com/muhze2 You can enable even default theme, Storefront for example.
If you want to place wishlist next to Add to cart button got to Wishlist > Settings > Position > Use shortcode. After that add the following code to child theme functions.php