Open your index.html file (usually located at public/index.html), add the following snippet to the end of your body tag:

<script type="text/javascript" src="<https://api.linkmole.app/backlinker.v1.js>" defer></script>

It should look something like this:

<!DOCTYPE html>
<html lang="en">
  <head><!-- OMITTED FOR CLARITY --></head>
  <body>
    <noscript>You need to enable JavaScript to run this app.</noscript>
    <div id="root"></div>
    <script type="text/javascript" src="<https://api.linkmole.app/backlinker.v1.js>" defer></script>
  </body>
</html>