Linking a Document is not called a Relationship and it is Under File Cabinet
Select the Result Dialog you wish to add the link to it should open the configuration.
At the bottom left Select MORE OPTIONS
Now Scroll Down is you dod not see any change......
Near the center Select the link Create New Relations
Name this Link
Selec the Item it is related to, in your example File Cabinet
Add the rules that would apply in your case
Then Save it,
