 Grab your AirTag with the white side facing down and the stainless steel side facing up. Press down on the stainless steel backing and twist it counterclockwise. You'll feel it loosen up. Pop off the back cover and there it is, the battery. Swap out the old battery with the new CR2032 battery. A pack of 10 is $6 on Amazon. When putting the battery in, you want the positive side facing up.