Marty, if you can open VuePrint in Win8 and use it's file menu to open the file you want to resize and you're finally looking at your picture in VuePrint . . .
Simply type the letter "Z" on your keyboard and a dialog box pops up (or again from the VuePrint file menu choose "Resize" and the same dialog appears). Choose to either make your image 800 pixels wide OR 600 pixels high and leave the checkbox labeled "Preserve Aspect Ratio" as you find it, that is checked (you want to preserve the aspect ratio). After choosing 800 wide or 600 high, if you then hit the Tab key (with "Preserve Aspect Ratio" checked), you will see the new value for the dimension you did not change before you click OK and the image is resized for you on the screen. You must still save the file under either the same name, or using "Save As" with a different name (you will wind up with two files using the second option, but the first is preserved as the file you started with.
In order to be uploaded onto the Forum, the image must be no larger than 600 High by 800 Wide AND be no more than 100 KB in size. Actually, anything over about 95 KB seems to trigger the "File too big" warning. So what I do is go out on the VuePrint file menu again to "Open" a file, and change the "View" to give me the details on the file size. If it isn't small enough after I've resized to 800x600, I'll either crop some of it off, or resize again at 550 high, 500 high, etc. etc. until the file will upload to the Forum.
Good luck, I'm sure you'll figure it out if you haven't already. Kraig may add some advice for running under Win 8; I'm still running Vista.