How To Set Harness :

=> Open Any Existing Flow And Unchecked Skip Create Harness From Process Tab Save The Flow.

=>Activate Rules Inspector ,After Run The  Flow

Display The OutPut Screen In YourScreen

=>Click On Top     "H " New Harness and Click On Save as Provides A class Group Name, Click On Save as

=>Select "Show WireFrame "Delete The Container(Top Container)

=>Create Your Own Section And  Drag and Drop Section On To a  Harness

=>Save The Harness, Go To Process Tab Of a Flow and Provide The Harness and Save the Flow 

And Run The Flow To Check The Output.