There's a component available now - feel free to customize it the way you want ...
See
https://www.opensource-socialnetwork.org/component/view/1971/footer-links

create your own theme
add the following line at the bottom of the ..._theme_init()function:

ossn_register_menu_link('facebook', '<i class="fa fa-facebook"></i>', 'http://facebook.com', 'footer');

Note: outer double qotes (") around params must be single ticks (')

consult the font-awesome docs for other available icons, and refer to line 20 of ossn.lib.menus.php for the params used by this function.

If you need more impact on the sort order of menu entries, you have to put your stuff into a little component instead. Because components (as the sitepages) are loaded AFTER the theme and of course you can't change something which is still not in place. :)