I think that tutorial makes it look harder than it is, but maybe that's because I already know how to do it!
Do you have a photo program that you're familiar with? Because essentially all you're doing is pushing the "print screen" key on your computer's keyboard (you may have to use "Shift" and "Print Screen" at the same time; for some reason I don't have to do that on my computer). That copies the image showing on your screen into the computer's memory (the "clipboard"). Then you just open up your photo program, create a new blank document, and "paste" the image on the clipboard into that new document. It's really easier than it sounds.