Using the Greenlee PDMM - 20 Pocket Multimeter is easy. First, turn it on and select the measurement mode you need, like voltage, current, or resistance. For non - contact voltage detection, simply bring the tester close to the suspected electrical source. When measuring voltage, make sure the device is properly connected to avoid incorrect readings. Keep in mind that this multimeter has a safety rating of Category III 300V, so don't use it for high - voltage applications beyond its limit. As for maintenance, keep it in a dry and clean place. Wipe it gently with a soft cloth if it gets dirty. Also, change the batteries regularly to ensure optimal performance. And remember, it comes with a Lifetime Limited Warranty, so if you face any issues, you're covered.