Twist clockwise one click for "Steady On" light, continue next click for "SOS" signal light, continue next click for "Flashing" mode or continue next click for "Off" position.
To change the battery, use a quarter or other flat edge tool to unscrew cap containing the battery counter clockwise. Remove old battery and insert new battery. Tighten cap by using same tool.
Replacement batteries available at most retailers. Uses one 2/3 A battery.