While there are a number of programs with which you can take screenshots of your computer screen, we have found that the best program is Jing. It's a free program for both Windows and Mac that also includes a free online storage account to which you can automatically annotate and then upload your screenshots (or <5 minute videos). Once it uploads (or saves to your computer), you'll then get a link to send to whomever needs it.
If you're able to attach files to whomever you wish to have the screenshot, you can use your OS's default screen capture feature.
You can take a picture of what is on your screen by pressing PRINT SCREEN (PRTSC or PRTSCN on some keyboards). This is called a screen capture. You can then paste the screen capture into a document, e‑mail message, or other file. There are two types of screen captures you can take: the entire screen, or just the active window. For example, if you have three programs open at the same time, you might want a screen capture of only the active window.
Windows 8.1 and higher
Press Command (⌘)-Shift-4, and then drag the crosshair pointer to select the area. Continue to press the mouse button, release the keys, and then press Shift, Option, or the Space bar while you drag to resize the selection area. When you are ready to take a picture, release the mouse button.
Pictures of the screen (screenshots) are saved as files on the desktop, but if you prefer to put a screenshot in the Clipboard, hold down the Control key while you press the other keys. You can then paste the picture into a document.
OS X 10.6 and higher