It took me a bit to figure it out too because when I first opened the file it gave me an error message, and then it looked like it was blank. But if you slide the slider, and also you can use your arrow keys, it moves through the file. One of the drop-down menus gives you a list of commands on how to move through the file. And another drop-down menu gives you the option to "copy input frame to clipboard" or something like that. Then you have to have somewhere to paste it, I think, so paste it into whatever photo-editing software you have.
Careful, though, it is very, very hard to stop once you figure out how to do it. I was up till 4 am playing, lol...
I saw that from your posts... that you were up at odd hours!