Special orders can only be placed for ‘Store customer’, a customer whose phone number is registered at the time punching the order (punch special or custom cake order)
Add Items to cart, click on the item which is added to cart 
Item edit POP-UP will come on screen > click on the item which is added to cart > click on ‘special order’ and select ‘Supplier’ > you can add any description or note if you want > click on ‘Save’ button.
Do the payment and print the bill.