do_action('addthis_widget',$url , $title, $style);
$url is the URL you wish to share. Generally, this should be get_permalink() if you are inside of the loop.
$title is the title of the URL you want shared. Generally this should be get_the_title() if you are inside of the loop.
$style can be either a string or an array. If it is in array, it should take the form of:
$customAddThis = array(
'size' => '16', // size of the icons. Either 16 or 32
'services' => 'hyves,joliprint', // the services you want to always appear
'preferred' => '8', // the number of auto personalized services
'more' => true // if you want to have a more button at the end
String can be one of the $addthis_new_styles styles listed in addthis_social_widget.php, 'above' (if you want what is chosen in the UI for above) or 'below') if you want what is chosen in the UI for below.