Firstly, you need to add a second price band  to the side dished to sell them at zero price.


Repeat this for every item as required


 


Now open the item you want to link the sub menu to. Check the use sub menus box and click on sub menus.



This loads the below screen. give the Menu a name and choose the relevant department by clicking department.



Change the Max to the number of sides you wish to give for free. and add the text "/IB2" To sell this item at zero cost, if you used a different price level that is fine just substitute the 2 for the price level you used at the start of this guide.  



Click Save.


Now when the clerk sells this item they are presented the below screen.



The one signifies they are allowed to choose one item from the choices.