First, Make your monitor shows on what you want to capture.
Second, Press the "Print Screen" button on your keyboard. This button is beside the "Scroll Lock" button, and near the F12 and Back Space button. It might be marked as "PrntScn" or "PrtSc" in some computer. This will take a screenshot of your full screen.
Third, Open the "Paint" software: Start Menu-> Programs -> Accessories -> Paint
Fourth, Paste the picture you captured in by press Ctrl+V in the paint window. You can use the Select tool in the Tool Bar of Paint window to select a region of the entire screen and right click to copy it.
After you copied the selected region, turn on another Paint window and press Ctrl+V to paste that picture in.
Then you can adjust the boarder of the picture to cut the write background by drag the square boarder
Finally, Save your picture to JPG type in your computer.