I'd be happy to help you out today. However, I will need a bit more context regarding your request in order to offer up any potential solutions.
Is there a certain Shipping carrier/service that you are trying to connect to your store. If so, which one?
Do you have your own negotiated rates through an account with this third-party shipping carrier? If so, are you wondering if you can connect your account to your Shopify store?
If there is anything else I can help you with, please let me know.
Dirk | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog