If it's got a pot, it's on the other side of the circuit board, next to the battery-contact/spring. The adjustment is 'backwards'. Counter-clockwise is more power, clockwise is less. But don't expect too much. These modules are usually set at the factory for maximum brightness. Turning it up past saturation of the crystal will only waste battery, create more heat and cause mode-hopping...
If you decide to play around anyway, Remember small adjustments, and note where it was set originally...
cheers,
kernelpanic