The easiest way to do this is using the Snipping Tool. The Snipping Tool is pre-installed with Windows, so you should already have it on your computer. The Snipping Tool itself comes with clear & detailed instructions, but in brief:
To open Snipping Tool, type Snipping Tool in the search box on the taskbar, and then select Snipping Tool.
To take a screenshot with Snipping Tool, select New, and then select the part of the screen that you want to capture. Choose from free-form, rectangular, window, or full-screen snips by selecting the arrow on the New button.
After you create the snip, you can draw on it with the built-in pens, save it, copy it, or email it to someone.
For more detailed information about the snipping tool, click HERE.