In order to map external shipping methods with the Walmart DSV channel please follow the steps below.
Step 1. Go to Set up- Channels- Walmart DSV- Shipping
Step 2. Click on "Add Shipping Mapping"
Step 3. Select the carrier you would be using for these type of shipping method.
Step 4. Select Mail Class for the carrier you have chosen.
Step 5. The list of Id's can be obtained by downloading "Carrier Labels and BOL's. List is directly provided by Walmart. If all steps are followed correctly all imported orders will display correct shipping method.
Step 6. Select corresponding "external ID" that matches the carrier ID and mail class.
End Result. Shipping has been successfully mapped for Walmart DSV. See example order below: