Open the Camera app on your Chromebook
Click the Launcher and search for Camera
Position what you want to capture in the frame
Click the shutter button to take the photo
Use the volume key or Enter key if your Chromebook supports it
Find the photo in the Camera app or in the Files app under Downloads
To take a screenshot instead, press Ctrl + Show windows
To take a partial screenshot, press Ctrl + Shift + Show windows
To take a screenshot of a window, press Ctrl + Alt + Show windows