You can add edit the Billing or Shipping address while making a transaction, by clicking on the Edit option, available under the ‘Customer name’, and further selecting the Edit Address option available on the right (‘Pen icon’). This address will be saved as your Billing/Shipping address for the contact.
However, if your customer has various branches and you wish to add a new address, apart from the Billing and Shipping addresses, you can click on the Add new address to add an additional address on the fly. This address will be saved to your contact as an additional address.
To know more about adding multiple addresses to a contact, click here.