How do I add/change a billing contact?

Your billing page can be accessed by clicking on "Account settings" in the profile image pop-out menu, bottom left of the main navigation on the left hand side of the screen and then "Billing". 

To add/change billing contacts, in the "Billing details" box against "Billing contacts", click the "Update" link to update this information.
Please note: you can add up to five additional billing contacts. A billing contact will receive all billing notification emails (subscription renewal invoices, payment card expiry warnings etc).