Go to administrative options..."Define orders and order sets".
Select each of the orders that you currently have that you no longer want, and hit "delete" after each. I think you need to delete one by one, but maybe you can select a bunch and delete several at one time.
Hit "Add new order" and type the order and the comments below it.
On the right, select "lab" if that is the tab you want the order to go under.
Hit "Add".