The favicon is the little image that appears on the tab for most pages.
Please get an ico file from the client.
Upload to file manager.
Go to viewer config and in the SEO metatags place the below code, substituting the image path for the relative ico file:

<link rel="shortcut icon" type="image/x-icon" href="publication.ico" />
<link rel="icon" type="image/x-icon" href="publication.ico" />
<meta name="apple-mobile-web-app-capable" content="yes" />
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />