Once you have shipped your product to the customer, either via an post standard post, royal mail, parcel force, dpd etc, you will need to notify the customer that the package is on the way to them.
You will do this by Creating a Shipment for the order.
Please watch the below instructional video which will take you through how to create the shipment and also show you what the customer receives once the shipment is created.
It is imperative that this is now completed for each order.
Video: https://youtu.be/M5SRDobLGME