When participating in the DSV program, sellers need to ship orders by using the exact shipping method and carrier that was requested by Walmart. Walmart covers shipping cost, and this is achieved by sellers using Walmart’s account for UPS and FedEx when generating shipping labels.
Walmart uses UPS and FedEx for shipping, only very few orders will have USPS requested as a carrier.
USPS does not provide accounts and subaccounts the same way FedEx and UPS do. In the rare cases when USPS is requested DSV sellers can use their own accounts and get reimbursed. The shipping reimbursement template should be requestsed by opening a support case in the Supplier Center.