When Salesforce turns on Chatter profile-based rollout for your organization, it adds the Enable Chatter permission to your existing user profiles and permissions sets. Enable Chatter is automatically enabled for all standard profiles. It’s also automatically enabled for custom profiles when any of these user-level permissions are enabled manually or as part of a license:
Modify your existing custom profiles with the desired permissions to control access to Chatter, and create custom profiles, if necessary.
Step 1 : Log in as a Salesforce administrator.
Step 2 : From Setup, enter Profiles in the Quick Find box, then select Profiles.
Step 3 : For each of your existing custom user profiles:
a) Click Edit.
b) In the Administrative Permissions section, select or deselect Chatter Internal User, depending on whether you want users with this profile to have Chatter access or not.
c) Save your changes.
Step 4 : If applicable, create custom user profiles with the desired permissions and assign them to users.