You can set the access permissions for each topic.
Click the More topic actions link found in the toolbar at the bottom of each topic.
Under Edit topic preference settings click edit settings for this topic.
Notice that you are in preferences mode rather than edit mode because the title will read Preferences forTOPIC . (In edit mode the title is all in blue and (edit) appears after the name of the topic.)
Add ALLOW or DENY settings.
Click the Update button at the bottom of the page. This updates the settings and returns you to view mode.
See AccessQuickSheet for examples of how to set access permissions.