There are two ways that I know of to "Enable" the "Relationship Viewing":
One is through your "Settings", under the "Permissions" 'Tab', in "FamilySearch".
The other is when you select the "Contact Name" of a User/Patron who has contributed details to a record.
Here is a "Knowledge Article" in 'FamilySearch'
How do I turn on or off the option to view my relationship to other users?
I hope this helps.