To install your customer support widget on a WordPress site, go into your WordPress dashboard and then click on Themes > Editor on the left side of the page. 

In the editor, locate the footer.php file in the list of files on the right side of the theme editor. 

In this file, paste the code snippet for your support widget just above the closing </body> tag at the bottom of the file. 

Then click Update File and the widget will be added to every page of your WordPress website.