You can pay by check, PayPal, or credit card. If you are paying by check, click the box "I will send payment by check.". To pay by PayPal or credit leave this blank.
To pay by credit card after you complete the process, you will be taken to a PayPal screen. At this screen you can pay by PayPal or scroll down to pay by credit card. If you close this window your registration will not be complete.