I usually just add in social icons manually.
If you take a look at the legacy theme in the footer, here is the exact code I used –
<div class="alignleft"><a target="_blank" href="https://www.facebook.com/StudioPress" rel="nofollow"><img width="48" src="http://demos.studiopress.com/legacy/files/2011/08/facebook64.png"></a></div><div class="alignleft"><a target="_blank" href="http://twitter.com/WesStraham" rel="nofollow"><img width="48" src="http://demos.studiopress.com/legacy/files/2011/08/twitter64.png"></a></div><div class="alignleft"><a target="_blank" href="http://linkedin.com" rel="nofollow"><img width="48" src="http://demos.studiopress.com/legacy/files/2011/08/linkedin64.png"></a></div>You can upload your images first, (WordPress uploader) then copy the links to those images and replace them in the code above right after src="
Then replace the link after href=" with the link to the social site.