At any time during the transaction click the Ticket button in the menu bar.
You can then click the Open Food or Open Liquor button depending on which is applicable.
Once the non-menu item menu appears enter the name you wish to give this item and then the cost of the item under that.
Once you are finished hit the Apply button.
If you get an error after you click Apply, please click here[TODO: Add Link to Setting Up Open Item Article]