1. Go to: Sales → Orders 

2. Open the order you want want to reorder

3. Click Reorder in the top right 

4.You can notify customer by email by checking "Email Order Confirmation" in the "Order Totals" block

5. You can also add order comments and append them to the order by checking "Append Comments" in the "Order Totals" block

6. Click Submit Order in the top right or scroll to the bottom of page and click Submit Order in the "Order Totals" block