You can add one tracking number to an order. Your customers will receive the tracking number by email.
To add a tracking number to an order:
1. In your Store manager, go to My Sales → Orders.
2. Find the order you want to assign the tracking number to.
3. Click Update Order and select Mark as Shipped:
4. Enter the tracking number and click Mark as Shipped.
The tracking number is sent to customers in the email with the subject Order shipped. You can edit the template of this email in Settings → Notifications.