1.) Go to Settings > Activity Feeds Configuration.
2.) Pick the account(s) you want to disable, and then click Deactivate.
Note: If you want to turn off activity feeds for multiple accounts, you can select as many as you like from this screen before you click Deactivate.
3.) A Confirm Deactivation window will appear. Click Deactivate to confirm.
You will receive a pop-up message to let you know that you will have to publish the entity for your changes to take effect. To do so,
4.) Go to Settings > Customization > Customize the System > Entities > Account > Publish.
This will publish your customizations. It may take a few moments.
When the customizations are published, then you can close the Account information window and go back to the account record. You should not see the activity feed any longer in your account record.
Congratulations! That is how you turn off activity feeds from your entities in Microsoft Dynamics 365 for Sales CRM.