Important: USB charging plug (input) is judiciously microUSB, same as most modern smartphones (Samsung, Moto ...). The output is a normal USB. You can use your phone's AC adapter to recharge the lamp, a single adapter to take on trips (and only one USB / MicroUSB)
how to use very simple: Connect the micro USB for charging, Blue LED: charged, Green: Charging
a detail: you must remove the small plastic washer that is on the battery inside before use (the washer makes sure that the device does not turn on during transport). Unscrew the lamp to access the rear battery.