To give a user permission to do this, go to Administration and either:
select Profiles to change a default profile, or
select an individual user and go to the Profiles tab in the user maintenance form.
Under the section heading 'Authorization' tick 'Share with users' and Share with folders' as required, and save the change.
Even when an item is shared, other users can only see the data they have permission to see, e.g., a user can't share a dashboard containing data about Branch X with someone who only has permission to view Branch Y.