Once installed (you will also need the .NET runtime framework - it's likely you already have this installed, but if not it can be downloaded direct from Microsoft), run the program from Start/Programs/IkonTools/ImageWatcher. Then simply enter or browse to the path of the folder you wish to watch for incoming images, select if you want to see the image filename and a histogram, and click "Go". ImageWatcher will then go full-screen (initially black) until an image file is written to the folder you specified.
Once the image is written, ImageWatcher will load it and display it full-screen with the options you selected. As soon as another image is written, that will be displayed, and so on. To exit the full-screen mode, simply hit the Esc key.