When you create an article, you can choose to display it only to other agents on your help desk using the Agents only option. These articles will be marked 'Private' and visible only to your agents.
To mark an article as private
- Navigate to the desired article, and open the Article Details page.
- Click the Edit icon in the upper-right area of the page

Under the Display Permission section in the right side, check the Agents only option.

Click Publish.
The article will be set as private and visible only to your agents. This particular article will not be available for your customers.