Find links shared with you in Safari on Mac
When friends share videos, news stories or other links with you using the Messages app, you can see what they sent in Shared with You in the Safari sidebar. (To see items in Shared with You, make sure Safari is selected in the Shared with You pane of Messages preferences.) You only see items shared with you by people who are in your contacts in the Contacts app.)
In the Safari app
on your Mac, click Shared with You in the sidebar (if the sidebar isn’t shown, click the Sidebar button 
in the toolbar).In the list of shared content, do any of the following:
Click content to see it in Safari.
Click the name of the person who shared with you to reply to them using Messages. You can also reply while reading the story — click the name shown just below the toolbar.