Using your G-Shock GA-2100 Series watch is a breeze. To set the time, simply find the appropriate buttons on the side of the watch. Press and hold them according to the instructions in the manual to adjust hours, minutes, and other settings. When it comes to water resistance, it can handle a 200 - meter depth, so it's great for swimming and other water - related activities. But avoid wearing it in hot tubs or steam rooms as the extreme temperature changes can damage it. For maintenance, wipe the watch with a soft, dry cloth regularly to keep it clean. If it gets dirty, you can use a mild soap and water solution, then rinse it thoroughly and dry it completely. This will help keep your watch looking great and functioning well for a long time.