This is a 5M42A, which should be similar to a 5M42. Pull the crown to the first detent (like you would to set the date). Now look at the picture that (hopefully!) is in this post. Just below the stem you’ll see a little white arrow pointing to a hole. When you put the stem in date set mode there is a little detent that appears in that hole. Press that in using a very small screwdriver or pin and then pull the crown out. Shouldn’t take too much force.

You can also pull the crown all the way out to stop the watch, but it’s a little harder to see the detent.

To put the stem back in slide it back in until you hear or feel a click.