I guess this will get buried but I've seen it come up a few times and I'd like to help. Please feel free to PM me if your device or Operating System is 'other'.
Windows 7
Start_Programs_Accessories_Snipping Tool
Drag a window around the required area
Save and name the file,
(If you right-click on the Snipping Tool in the menu, you can add it to your taskbar for easy access.
IOS devices (recent models)
Hold down the Home button and Power Switch simultaneously.
The screen will light up and a clicking sound can be heard. A 'photo' is taken of the current screen and saved to your images.
Google Chrome (& some other browsers)
"Awesome Screenshot" browser extension. (Search for the appropriate one for your browser)
A great tool. You can crop, edit & annotate screengrabs.
Save as a .jpg file to your hard drive and upload.
Hope this helps. Please feel free to PM for any additional tips