Installing gamification software into WordPress

Im new to WordPress and wanted to install an open-source reader loyalty/engagement API into a clients website. The documentation is pretty straight forward, but I dont know where to install the php library. More documentation and the Wiki for the software can be found at code.google.com/p/userinfuser

PHP Documentation is as follows(partial):

Class UserInfuser($account, $api_key)

public function get_user_data($user_id)

public function update_user($user_id)

public function award_badge($user_id, $badge_id)

public function remove_badge($user_id, $badge_id)

public function award_points($user_id, $points_awarded)

public function award_badge_points($user_id, $badge_id, $points_awarded, $points_required)

public function get_widget($user_id, $widget_type)