• Connect to your webserver via the FTP program of your choice, and navigate to whmcs/template/X, where X is the name of the theme that you are using in WHMCS.
• Find the file  footer.tpl  and click on it.
  
• From the left side of your  cPanel  click on  Edit File  or  Edit File with Code Editor  option.
  
• At the bottom of the page right above the tag put:
  

• When adding JavaScript to a WHMCS site, you need to add these {literal} {/literal} tags before and after the JavaScript. 
  
• Click  Save changes  (upper right corner of page.)
  
• Exit  from cPanel.

To get the Zoho SalesIQ chat widget code snippet

• Login to your Zoho SalesIQ Operator console.
  
• Navigate to  Settings > Brands > { Your brand name } > Installation > Website.
  
• Click on Copy this code to copy it and then paste it on your website's HTML source code.