Congratulation, how exciting!
To send your customer an email notification with shipping information, click on the "Order" > "New Shipment."
Here is where you can enter a tracking code to let the customer know their order has been shipped.
Upon shipping an order, be sure to update the status in your dashboard from PROCESSED to COMPLETE. This way, you can keep track of your sales. You can do this by clicking on "ORDER" > "VIEW ORDERS". Hover your mouse on the green button on your order list, and you can update the status accordingly.
If you want to restock an item, be sure to update the inventory on your listing page. If you have sold out of something, you may want to remove the listing or mark it as hidden, or include in your description that more will be made, and ask your customers to check back.