Having a Purchase Order means that you already checked out items you wish to pay (conference registration fee). This does not mean you already paid for it. You have to click on the Paypal button (Click here to pay in Figure 1a) found at the upper left hand corner of the Purchase Order to proceed with online payment at the Paypal website to finalize your registration. Otherwise, your online registration transaction will be treated as temporary and you may lose your slot.

After clicking on the button, you will be prompted to enroll a Paypal account by entering your credit card details to safely pay online. This is much more secure than entering your credit card details directly on to the website other than Paypal. (Note: Make sure you have a credit card such as Visa, MasterCard, Discover, and American Express to be able to create a PayPal account)

The PayPal Sandbox is a self-contained environment within which you can prototype and test PayPal features and APIs. The PayPal Sandbox is an almost identical copy of the live PayPal website. Its purpose is to give developers a shielded environment for testing and integration purposes and to help avoid problems that might occur while testing PayPal integration solutions on the live site. Before moving any PayPal-based application into production, you should test the application in the Sandbox to ensure that it functions as you intend and within the guidelines and standards set forth by the PayPal Developer Network (PDN).

Get Started Quickly: Integration Center
PayPal’s Integration Center at https://www.paypal.com/integration has step-by-step details for getting started with the PayPal Software Development Kits (SDKs), Website Payments Pro, Express Checkout, Website Payments Standard, Authorization & Capture, Instant Payment Notification, and more.

Visit the Integration Center at: https://www.paypal.com/integration