Gather a small screwdriver, case knife or pry tool, tweezers, and a replacement battery
Place the watch face down on a soft cloth
Open the watch case back using the correct method for your watch
Note the battery type and orientation before removing it
Remove any battery clip or retainer if present
Lift out the old battery with tweezers or a nonmetal tool
Insert the new battery in the same orientation
Reattach any battery clip or retainer
Check and replace the gasket if needed
Close the case back securely
Set the time and test the watch
Take the watch to a professional if the case is sealed or difficult to open