It will pop apart. There are a few styles. Some have more screws. This indeed has one.
Im right handed. So in my left hand I hold the upper part of the shell with the button and cord upwards. Then with right hand, I lift out on the end were the screw was and pull firmly downward (again, cord it upward) and wiggle back and forth. It will pop apart. Once apart, you will see how it goes back.