To select or update the receipt printer for a particular device go to the admin screen and press "Printers"
You will see a list of printers that you have previously added to your system. If the printer you want to print food to is not in this list you can see how to add it here.
If the printer is in the list, press on it to go to the edit page.
On the edit page you can select "Receipts" under "This device" on the righthand side.
When you have finished pressed "Done", and then press "Save".