In order to submit a test order, first create a discount by going to the left hand side of your storekit dashboard, then go to
Discounts > Create a discount
Enter a Discount Code for example test100 and set Discount type to Percentage with a 100% Discount value.
Now, apply the Discount to the Store you're testing. Open your store URL and place an order as if you're a customer.
At checkout, apply the code that you've created and place the order.
The order will appear on your Live Orders. If you already have a printer linked to your store, the order will also print.