index.html

<html>
  <head>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css"><link rel="stylesheet" href="./node_modules/@formio/js/dist/formio.form.min.css">
    <script src="./node_modules/@formio/js/dist/formio.form.min.js"></script>
    <link rel="stylesheet" href="dist/formio-pretty-checkboxes.min.css">
    <script src="dist/formio-pretty-checkboxes.js"></script>
    <script type="text/javascript">
        window.onload = function() {
          Formio.icons = 'fontawesome';
          Formio.use(FormioPrettyCheckboxes);
          Formio.createForm(document.getElementById('formio'), 'https://examples.form.io/checkboxes');
        };
      </script>
  </head>
  <body>
    <div id="formio" style="padding: 2em;"></div>
  </body>
</html>