You can simply change an address to an already-placed order. Please follow the steps below:
- Go to Orders tab and find the order you want to change the address to
- Click on the order number which is displayed in green under the Order column
- Click on the button in the box which is located to the right of the order, in line with Delivery to
- Edit the requirements and press Save
Additionally, you can follow the above mentioned steps to edit the Invoice Address as well.