Paste the code to you WooCommerce store’s HTML field.
Next, go to your WooCommerce store and find the HTML field. It is most likely in the form of an HTML/Code widget or module which you can find on WooCommerce’s dashboard. Add it to your page, and paste the code you’ve copied before to the HTML field. Save and update, and that’s it, you should have Common Ninja’s What's New Popup plugin on your WooCommerce store.