I used this code in footer. But it must be a stacks page with the FontAwesome stack from Joe Worman, as @zeebe wrote, or @kryten 's code in header section.
Or the theme support this feature!
With my code the icons are linked to the desired website.
<a href="http://www.desired_site.ch"><i class="fa fa-camera-retro fa-lg"></i></a>
