As Bob said, you need to get the canvas set up first. I was under the impression that you had made it that far with no problem. But if you can see the image updating in the Video Feed Setup, there's no reason why we can't get the canvas working.
Go to your canvas properties and click on the "Graphics" tab. I've posted a screenshot of my settings (I have the Weather Edition; your demo version will probably look different).
In line 1, double-click in the white box below the "Enable" heading (on my screenshot, it says "Yes" in that box).
Move across to the box under the "Update Interval" heading. I'd suggest putting a "1" in that box, which tells ImageSalsa to retrieve a new image every 1 second.
If you're using a USB camera, you will use the video feed for your canvas. Click on the box under the "Video Feed" heading, then go to the drop-down menu below the tabs and select a video feed. You will probably only have one to choose from. Mine says "Microsoft WDM Image".
Move left to the box under the "Source Type" heading. Repeatedly double-click in that box to cycle through the available options. Hopefully you will see your camera's image, probably using the "0" setting.
Hopefully this will work.