To view Commlytics for a Teams Chat or Channel, first open the Chat or Channel that you want to view the Commlytics for.
At the top of the screen, you should see a few tabs, such as 'Chat', 'Shared', and perhaps some others. Next to these, there is a button with a plus sign (+). Click on it.
This button lets you add a tab to access others installed applications that are integrated with Teams. You should see Commlytics along the top, but if you have a lot of apps you can start typing 'Commlytics' in the search bar until it shows.
Click the Commlytics app to create a Commlytics tab at the top. You can now access Commlytics for this chat or channel at any time by clicking on the tab.
Note that creating a new tab in a Channel or Chat creates the tab for ALL members of the Chat or Channel.