CYC uses an external service, not on this website, to manage its billing and collection. This is as much to assure your financial security as it is to assure that this portion runs correctly and is not subject to error. The main, public-facing, site, that you are looking at now is an all-volunteer (aka "Corinthian") operation that operates at a significantly lower level of security.
To check your bill, you may simply click on the "Check My Bill" button when logged in to this site. Credentials exchanged between the public CYC site and the accounting site will give you access.
To PAY your bill, you may either click on the button on your statement from the link above, or click on the "Pay My Bill" link. That will take you to "E-Payment" which will require a NEW login and operates at a stronger level of security. One tip, they will ask you for your membership number. It should be five digits, so add zeroes to the front to get there.
Support: The bill-checking and bill-paying sites are under the management of the CYC accounting department, and you will need to contact them at 415-435-4771 with any issues.
To log into the main CYC site, however, you may simply click the login button at the upper right of the screen, or click here. You will either need your CYC.org username and password OR your name and membership number to log in.