I will give you SSH/sftp details in the private section so downtime of the pages is minimal and you can make the changes yourself.
The site uses a child theme so you will need to navigate to the appropriate folder to access functions.php
Can you add the link to the staging site? Add the code there as well
Please take note that this inquiry is more related to WordPress as opposed to GeneratePress itself. It’s not part of our scope of support but we’ll do our best to assist and point you towards the right direction.