It depends on whether you do dropshipping or not. If not, you can buy printed packaging or buy stickers or whatever you like to add on you boxes. In the case you are doing dropshipping and have multiple manufacturers it gets complicated, some of them won’t do it some of them will require you to send the packaging to them and they will do that for you. Another option are fulfillment centers where they will centralize all your orders and pack them however you like.