As the title states - Shared Data Stories simply mean the reports shared with you by another user in your organization.
To share your data stories:
Step 1: View the desired data story to be shared
All your data stories can be found under 'My Data Stories' in 'Data Stories' tab
Step 2: Sharing your Data Story
Click on the share button in the top right corner of the Data Story
Set read/write permission and share
To view all your shared data stories:
Go to the 'Data Stories' page
Click on 'Standard Data Stories'
Read next: