Hello @com4digital,
The menu in the demo is constructed using the WooCommerce plugin which is recommended by the theme itself.
So at first activate the WooCoomerce plugin then add new products/ food items by going to Admin Panel > Products > Add New.
Screenshots:
http://prntscr.com/ixzcwc
Finally go to Admin Panel > Appearance > Customize > Homepage Sections > Items Menu Sections and select ” Woo Product category” in Content Type option. Then chose the category that you have assign to the food item which you have created from Products menu.
Screenshots:
http://prntscr.com/ixz9l4
Hope this helps.
Best Regards!!