While you are still figuring out how the widget is going to look from the end user’s point of view, here is a simple trick to help you test the widget. That too, without needing any help from a developer.
Follow these steps:
Add following HTML code in the HTML section
<h1> This is a test page </h1>
Make sure that <script> </script> tags appear only once)
Now the widget will load in the preview section. Click to expand.