How to change a watch battery.
In order to replace most batteries you will need a case opener and tweezers, always make sure you rest the watch face on a soft towel to avoid scratches to the face. Case openers are very useful as they come with different pins to fit different screws, the handbook should tell you which pins to use. You adjust the pins by moving the wheel and handle. Most backs will twist clockwise to unscrew, but a few will go anticlockwise, again the booklet should tell you this. Once you have the back off, simply use the tweezers to carefully lift out the battery.