Where can I change my billing address?
You can find your billing address in your account settings. You can access the settings via your profile picture in the top right-hand corner and the Account menu item, or by clicking on Finances in the left-hand menu and clicking on the "Billing Address" button in the following screen.
In the settings, you can simply change and save the address.
If you're looking to add a separate mail address for accounting, read this article.