I keep getting the following error

Warning: require_once(Services/PayPal/Type/XSDType.php) [function.require-once]: failed to open stream: No such file or directory in /home/.faulkner/chhaymam/store.chhaymam.com/pear/Services/PayPal/CallerServices.php on line 15

Fatal error: require_once() [function.require]: Failed opening required 'Services/PayPal/Type/XSDType.php' (include_path='/home/.faulkner/chhaymam/store.chhaymam.com/pear:.:/usr/local/php5/lib/php') in /home/.faulkner/chhaymam/store.chhaymam.com/pear/Services/PayPal/CallerServices.php on line 15

I think i setup the "API Certificate File" wrong, i copied the code into text and renamed paypal.pem. Does anyone know any good tutorial on how to set "API Certificate File" and its pathway.