Go to shop's Checkout settings, page, found at this URL: https://[store domain]/admin/settings/checkout
Note: You must replace "[store domain]" with the actual domain for your store.
Add the following single line of HTML (<script>
tag) on the Checkout settings page, under the section: "Order Processing" -> "Additional Scripts"
<script type="text/javascript" src="https://inflooense.com/js/platform/inflooense-shopify.js"></script>
Go to your site's Theme editor.
First, visit this page: https://[store domain].myshopify.com/admin/themes (again, replace "[store domain]" with your store's domain name)
Then, click the "Customize Theme" button. Next, on the left-side of the page's navigation menu, click More Actions -> Edit Code
Add the following HTML into the theme.liquid page, just before the </head>
closing tag (please use the Find feature in your web browser to locate this exact text!).
then click the "Save" button:
<script type="text/javascript" src="https://inflooense.com/js/platform/inflooense-shopify.js"></script>