Engagement Engine Editor will only be usable by organizations that have tagged their pages with the ATGSvcs JavaScript tag (atgsvcs.js).
An example of such a tag is:
<script type='text/javascript'>window.ATGSvcs = {'uoid':
account ID number};</script>
<script type='text/javascript' src='//static.atgsvcs.com/js/atgsvcs.js'></script>
This tag should be on each page within the website as it is required in order to provide continuity and ensure a complete history when using conditions such as Page URL History or Search Engine.