If you are on your desktop computer and cannot see your computer screen on the Smartboard or TV, check the following

Press the Windows key on your keyboard (between the Ctrl and Alt button on the bottom left) and the P key.
You should see a menu appear on the left of your computer screen, choose Duplicate, and hit Enter
if this is correct, and you still cannot see your display,
Check the input selection on your SB or TV. Make sure the proper HDMI connection is selected.
if this is correct, and you still cannot see your display,
Make sure your device is really connected to the SB or TV with the proper cable