include("sailthru/Sailthru_Client_Exception.php");
include("sailthru/Sailthru_Client.php");
include("sailthru/Sailthru_Util.php");
$sailthru = new Sailthru_Client([YOUR SAILTHRU API KEY], [YOUR SAILTHRU SECRET]);
You can find your api key by going to this page and clicking on the lock next to "API Key / Secret".