This post explains in detail how to add a favicon to your White Label.
To add a favicon to the White Label page, open the "Meta" section in the settings of White Label and post this string in the form:
<link rel = "shortcut icon" type = "image / x-icon" href = "PastHereLinkToFavicon">
Repeat adding code for each page type (Front, Flights SERP, Hotels SERP, Hotel page).
Note! The image should be available on the Internet, and not be only on your local computer.