Create Application within Shopify for 3PL API

We need to have a small Application developed to have Shopify talk with our 3PL company. The Application needs to synchronize shopify and our 3PL company and send unfulfilled orders that are marked as paid and non fraudulent either automatically or manually via user setting. Once the 3PL has fulfilled the order and supplied a tracking number then it should automatically fulfill the order in shopify and advise the customer of a tracking number with a link to the appropriate carriers tracking screen. API information has been attached, for what we are told is a fairly simple setup. This needs to work in conjunction with Tradegecko