At main menu click on Settings >> Order settings tab
Order settings
Default order template: The order template that is set for new orders (you can change it per order) You can preview the look of the selected template
Order prefix: Order numbers may optionally be prefixed with a group of letters (P.E order number may be: ORD10001)
Starting order number: if there are no orders recorded yet then this will be the first order number
Customize order text labels: if you would like to change the various texts that appear on the printed order, modify these values.
Predefined terms and conditions text: the default terms and conditions text that is set for new orders (you can change it per order)
When you've finished editing the fields, click on "Save settings" toolbar button.