Adding tracking information to an order
From your Shopify admin, go to Orders, then open an order that has a fulfillment status of Partially fulfilled or Unfulfilled.
From the order details page, click Fulfill items (if rather than this you see an option to Buy postage and fulfill items, you may click Continue next to it instead):
In the Tracking information section, enter your shipment's tracking number:
Shopify might recognize the tracking number format and choose a shipping carrier for you. If it doesn't, or if it chooses incorrectly, then choose your shipping carrier from the Shipping carrier drop-down menu. If your carrier isn't fully supported by Shopify, select Other:
Finally, click Fulfill items:
If you selected "Other" as your Shipping carrier, from the order details page click on More actions > Order lookup. On the next page, select the Shipping company from the drop-down menu, then click Save: