List fields are used in Classic Contact Forms
Steps
Select My Apps in the top menu
Go to Lists in the My Apps sub menu (if you don't see Lists appear, reload the page)
You arrive on the Manage Lists page
Select Create new list
On the Create new list page
ensure that each item in the List has a different Priority number
Each priority number should increase sequentially from 1
click the Add item button to add new items to the List
In the Advanced Options section you can optionally choose which Ratio Set Category to add the List to
Press Save