To find the billings page please log on to cap desk and go to 'Settings' --> 'Billing' as seen below. This is also where you can find your invoices from Capdesk, on the right-hand side of the screen.
From here you can update your Billing information using the green Edit Billing Details button.
This will bring you to this page below where you can fill in your details.
To edit other Company information on Capdesk, please see these articles: Company Settings