Step 1: Go to Media Tab
Click on Media under Side-menu
Then click on the Upload Button.
Step 2: Cast Image/video
Click on the Action icon, then on Cast.
Select Screen
Select screen box will appear, click on the screen where you want to display your image/video.
Then click on the cast.
Step 3: Cast Successful
Your image/video will be successfully cast to the selected screen.
Check on Paired Screen, your image/video will be displayed there.
Video Guide on How to Cast Image/Video to a Screen