Provided that you haven't hidden the Firm Feed, it can be found in the following locations:
The "Firm Feed" sub-tab of the "Dashboard" page.
Matter Details Page
A Matter-specific firm feed, called the "Timeline", exists on each Matter.
Clio Connect Contact Card
Additionally, the "Firm Feed" sub-tab can be found on the Contact card for any Contact that is also a Clio Connect user.