You can change the favicon that resides in the browser tab of your Help Site FAQ to something you currently use.
Go to "Brands"
Click on "See all settings" for the brand you'd like to edit
Click on "Custom Header and Footer"
In the "Meta" section, enter
<link rel="shortcut icon" href="https://yourwebsite.com/favicon.ico">where the link points to the URL of where your favicon lives.