Using your Fenix TK35 flashlight is easy. First, choose the right batteries - you can use two 18650 rechargeable batteries or four CR123A batteries. Make sure to insert them correctly to avoid reverse polarity. The dual tail switches let you quickly adjust the brightness levels or switch to the flashing modes. For normal use, pick one of the 5 brightness levels according to your needs. If you're in an emergency, use the strobe or SOS mode. When it comes to maintenance, keep the flashlight clean. Wipe it with a soft cloth after use, especially if it gets dirty during outdoor activities. Store it in a dry place. Also, pay attention to the low - voltage warning. When it goes off, replace the batteries promptly to keep your flashlight working well.