Paying an Invoice
Sign into the site using your email address and password. (The site will have emailed you a password when you registered. This password you can change once you sign in. Click edit profile, make your changes then click save)
After you sign in and accept the site waiver you will arrive at your My Profile page. Similar to the picture below.
You can click on the "Pay online" link button or on link to view your invoice "invoice #00000" that will have the same link button available to you.
When you click the "Pay online" button you will be taken to the following page where you can sign into your Paypal account or if you wish to pay by credit card click the "Don't have a Paypal account?" link which will take you to the credit card payment page. (next picture)
Credit card payment page: fill in the blank follow the prompts and you are done.