Learn how to create sandbox accounts within your PayPal developer account so that you can fully test your applications prior to launching them on the live PayPal servers.
Create your own developer account at: http://developer.paypal.com
Get PayPal documentation at: https://www.x.com/developers/paypal/development-integration-guides
Get direct developer support at: http://www.paypal.com/mts
When you're ready to go live you can obtain your credentials here: https://www.paypal.com/us/cgi-bin/webscr?cmd=_login-api-run
