How to add Javascript as PopUp content?

I have never added Javascript to WordPress before. I was given a javascript link by a form company. In Pop Up, I clicked on the Text input box and entered:
<script type="text/javascript" src="//"></script>

The src information is what the company provided.

I set Javascript for all settings.

On the main page, I see the Black X showing that a Popup is loading but nothing in the box.

If I add this in a Post or Page, it displays an entry form.

Is there something else I need to enter for Pop Up! to work?

Thank you for your help.