From the Home screen, tap the Apps icon (in the QuickTap bar) > the Apps tab (if necessary) > Camera .
OR
Tap Camera from the Home screen.
OR
With the backlight off, touch and hold the Volume Down Key (on the back of the phone).
If you’ve set your phone to use the Swipe unlock method, from the Lock screen, simply press the Power/Lock Key (on the back of the phone), then drag the Camera icon upward to open the Camera app.