On a PC
To capture a screen shot or an image on a Windows PC, just press Print Screen, or PrtSc. If you just want the window you are in press combination of keys Alt + PrtSc. The image will be saved in your clipboard, so the new main paste it in a word document or within a drawing program. If you want the image saved automatically, press Win + PrtSc combination. Your screenshots will be saved to your default directory ( usually the Desktop)
On a Mac
To capture a screen shot on the Mac, press cmd + Shift +3. Your screenshot will be saved to your desktop. Alternatively you can press cmd + Shift + 4 and drag the crosshairs to the area that you wish to copy. This screenshot will be saved to the desktop as well.