To access strobe
a) Turn on the light and tighten the head. The light should be at the brightest setting.
b) Twist the head (the black part) to the lowest level and tighten the head again within 1 second. The light shall start to strobe.
c) Repeat step 2 to access other auxiliary modes.
The best way will be searching "D25LC2 TAC" in the youtube channel. You should find details there.