Help. I unpinned my participants' screen

[LarryPeterson24]

When I conduct a meeting, there is an icon at the bottom of the screen called Participants that shows the list of active viewers in the meeting room.  This list is pinned to the side of the view screen and maintains its size and location throughout the session. 

I accidentally unpinned the list from the side of the view screen.  Now, the box is of small size and doesn't fill in the empty space.  How do I pin it back to the side of my view screen to keep a constant size?