Checkout video user guide from the below link.
If you are not using the Shopify's native fulfillment settings, but still your need to send order status notification to your customers, you can do it with Pickeasy.
To do so, click on the “Customize Actions” option in the Pickeasy's homepage.
Then, check both "Enable Ready Action" and "Enable Fulfill Action" to send notifications.
If the order is ready then click on the required action based on the order’s fulfillment method.
If the fulfillment method is "Store Pickup", click on "Ready for pickup". Then, the ready for pickup notification will be sent to the customer via email.
If the fulfillment method is "Local Delivery", click on "Out for Delivery". Then, the out for delivery notification will be sent to the customer via email.
Once the order is picked up or delivered, you can change the status to "Fulfilled" and you can close the order.
The default email will be sent from shopify.