how?
well, i did it in more ways than one.
First by adding html code to the beginning of the display templates. But thats messed up the menu in this theme.
Then I simply downloaded the favicon package from SMF. Uploaded an image with the name ' favicon.ico ' and then chose that image as my favicon within the admin section.
I think firefox automatically loads the ' favicon.ico ' image and displays it, if you have it in the main ftp directory.