You can enter Buy Shipping preferences for specific ship-from addresses using carrier
Next to an order, click Buy shipping, and then
click Buy Shipping
In the Carrier prioritization section, click Edit. A preferences page will appear.
Drag the carriers you prefer from right to left into the numbered spots.
If there is a carrier you prefer not
to use, leave the name in the section to the right.
Based on this prioritization, Buy Shipping selects the lowest cost shipping service your
carriers offer that meet the required delivery date.
For more information about linking carrier accounts, see Manage your carrier accounts.