Most businesses have unique shipping needs that are based on a variety of factors and limitations. Once you've decided which methods (and/or carriers) to offer, the only thing your shoppers need to do is choose a method when they place their orders. As part of the third-party fulfillment setup process a mapping must be created from each available shipping method option to a unique shipping code used by your fulfillment provider.
To gather shipping methods from BigCommerce:
Click on Setup & Tools>Shipping.
Click on Edit for the Zone of choice.
Click on Edit next to the shipping charges types that have been setup. eg. Fedex or UPS
Specify the information and select the service types that will be applicable. eg. Standard Overnight, First Overnight etc.