How to make Popup Pro + Getresponse newsletter form work together?

Hello,

we would like to have a newsletter pop up. I have installed Popup Pro and tried to make it work with the plugin from Getresponse.

The Getresponse widget does appear in the content space of Popup Pro as a drop down where one can choose the form made in Getresponse, but this way the pop up just shows empty. The support in Getresponse told that the plugin only works in default wp themes, so I guess that's the reason why the widget doesn't work in upfront.

They suggested to use a java script block of the form, which looks like this:
<script type="text/javascript" src="http://app.getresponse.com/view_webform.js?wid=11757301&u=KqHV"></script>

Where should I add this script in order to have the form work in Popup Pro?

Thanks so much for your help!