Shopfront allows you to add multiple billing addresses as well as update already saved addresses.
If you only have one billing address, it will automatically be set as your default billing address. However, if you have multiple billing addresses saved on your account, you may decide to change your default billing address.
In your Address Book, each address is in a separate box. Each box should have a Make Default option in the top left-hand corner. Select this option to make a particular address your default billing address by clicking on the Make Default button.
You will receive a message confirming the update and the address you chose will now show as your default billing address.