The iMac comes standard with a built-in iSight camera that allows you to take pictures and capture video with native Apple applications such as Photo Booth. After you take a picture on the iMac, Photo Booth allows you to preview the photo directly through the program interface. Photo Booth saves pictures as JPEG files in the "Photo Booth" section of your main "Pictures" folder.
Click the "Spotlight Search" icon at the far-right of the menu at the top of your screen.
Type "photo booth" into the search field, then select the application from the list of results that appear.
Wait as Photo Booth opens. The iSight camera activates. The Photo Booth window displays the image in front of the iSight camera.
Press the red "Shutter" button below the displayed image. Photo counts down for three seconds, then takes the picture. A thumbnail of the picture appears at the bottom of the program window.
Click the thumbnail to preview the picture.