Paste the code to you Magento store’s HTML field.
Next, go to your Magento 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 Magento’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 Image Magnifier extension on your Magento store.