How to make a virtual join editable

Hey experts, 

I'm trying to make a VJ form editable, and was looking at an OOB form that makes a VJ editable but I'm confused about the steps to recreate it. 

Here's the out of box VJ that is editable, but when I click on the link record there's nothing in there and i'm confused about what goes in as the target file name and the target field name