just paste this code in “Script in the body”
<script type="text/javascript">
document.addEventListener('DOMContentLoaded', function() {
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = '//cdn.callrail.com/companies/*******/4b1f35b918a351fe5d51/12/swap.js';
document.body.appendChild(script);
});
</script>