If you look at your keyboard, you will find a button, probably on the right side of your screen, that says "Print Screen," or "Prnt Scrn," or some other variation of the spelling. This was the button that used to actually be used to print what you were looking at on your monitor. The button still works, but in a different way.
Notice that it is probably on a button that has two options, the Print Screen on the top and another beneath it, usually in light blue print. Now look down below at the left bottom of your keyboard. There is a white Ctrl button and a blue printed Fn button. One is Control and is for the top option in the two option buttons and the other is for the bottom options.
Make sure you have an image or picture editing software on your computer. Something as simple as the normal Paint software almost always included with computer's software works great.
Look at your screen and center the picture or file that you want to copy. If you are sending a copy of what is on your screen to someone, check to make sure that you don't have any personal information showing down below on your taskbar.
Hold down the Control button (Ctrl) and then the Print Screen (Prnt Scrn) button. This will tell your computer to copy the screen information as a picture to your Clipboard.
Open the picture software you wish to use and then either place your cursor on the open template, right-click your mouse and hit "Paste." Alternatively, you can hit "Edit" and then "Paste." An exact replica of your screen should appear.
Save the image to your picture file and give it a name. You can now send it as an email attachment or do whatever you want with it.