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Create a Zendesk Chat account
Once logged in, navigate to Settings > Widget > Getting Started.
Copy the "Embed the Zendesk Chat Widget" script.
The script looks similar to following snippet:
<!--Start of Zendesk Chat Script--><script type="text/javascript">...window.$zopim...</script><!--End of Zendesk Chat Script-->
Navigate to TitleLeaf Admin > Management > Settings.
Paste the script into the "Chat Script" field in the "Other" section of the "Settings" page.
Click the "Save" button. The widget should now be visible at the bottom of the public site.