add the following into your skins storyindex.tpl file I suggest putting it under the chapter list

<a href="/recform.php" target="page" onClick="window.open('','page','toolbar=0,scrollbars=0,location=0,statusbar=0,menubar=0,resizable=0,width=550,height=470,left=50,top=50,titlebar=yes')">Recommend this story to a friend!</a>