You can control who has permission to view stories (also known as updates, survey responses, post event updates, timeline updates) by changing the story’s privacy level. Every story has a default privacy level which is set on the project’s preferences page.
Steps
Go to the Story page of the story you want to restrict access to
On the Story page, select the padlock icon
A dropdown list appears that lets you select your preferred privacy level for that story
When you select Only certain individuals a popup appears that lets you choose the specific users whom you want to permit to view the story
Press Save.