You can change any order's shipping address prior to label printing.
To do this, expand the order in ReadyToShip, and edit the address fields. Then print (or update) your label.
If you wish, you could add a note or edit the address back in your store's original order as well.
Note : Order addresses that are modified in your store will not be imported by ReadyToShip as ReadyToShip does not get notified when these changes are made. It is important to change any shipping address in ReadyToShip.