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)