1. To restrict a Topic to one or more Groups, click Communication (next to Content on the Navbar).

2. Click Discussions (the last option on the drop-down menu).

3. Click the down-arrow next to Topic.

4. Click Edit Topic (the third option on the drop-down menu).

5. Click Availability Dates & Conditions (the first box on the right).

6. Click Manage Restrictions.

7. Click Restrict topic.

8. Select one or more Groups under Discussion Groups. For example, Group 1. 

9. Scroll down and click Add (blue button).

10. Scroll down and click Save and Close (blue button).

11. That's it. You're done.

Interactive tutorial