I checked with a jeweler and he said that you pull the stem out and that releases the crown where the battery can be accessed....he advised to let a jeweler do it.
Sometimes you can't do it yourself. It takes a special tool that only a jeweler has. Turn over the back and if it has little notches that takes a special tool. If it is flat you maybe able to pry it...
The back pops off on some watches. You can go to a watch store and they can put a new battery in it for you. Some others don't need a battery though. On these types when you move your wrist, the time...
first, remove the 4 screws on the back of the watch (but you knew that part)
take off the cover.
You will probably need to take the watch out of the casing which is a little tricky but it can be...