To access your ship method mappings, go to Setup > Customization > Record Types > Magento Ship Method Mapping > List (or View Records).
This mapping is used in the Magento Order Import to set the Ship Via field in NetSuite. This mapping is different than the Carrier Mapping in that it maps ship methods in Magento (stored at an order level), as opposed to carrier codes (stored at a shipment level).
Unfortunately, Magento does not supply a place to view all possible ship method values they will send us. To work around this, you must place a test order (or wait for a real order) to import that contains the ship method. The connector will not initially be able to import the order because the code is not mapped. However, it will throw an error on the Celigo Job Import page (shown below), and the code from Magento will be listed. This code (for example, flatrate_flatrate) can then be added to the mapping list above.
Note: when mapping new entries (or changing existing ones), please be sure to refresh integration caches when you are finished.