Shopify Shipping doesn’t support DDP labels, so you are required to get a shipping account from the carrier.
You can visit the carrier’s website to find more information on how to create an account. The good part is that many of the major carriers offer discounts for small and medium business owners.
I recommend talking to DHL, UPS and FedEx to negotiate your rates.
Once the account is created, you can directly go to the carrier’s website to generate a DDP label and mark the order as fulfilled in Shopify by providing tracking numbers. When you have more shipments, you can automate the process by using an app.