Add facebook like box social plugin

Hi. I recently started building my blog and chose the Clean Journal theme because it looked really good and had great customization. I was wondering how I can add a facebook likebox to my sidebar? I have tried different plugins for facebook social plugins and also tried to add that piece of code into the header.php file after the opening body tag, but none seems to work. Can you help please? My website is http://mikaelgunther.com Best Mikael