The middle part slides out.
There are openings on two sides. One side has a larger opening than the other.
Once you gently slide it out, you'll see the two
batteries. Make sure the positive side is facing up when you put them back in.
Just firmly push in on the tab that's on the side with the smaller opening.
What you'll be doing is pushing it through, kind of like a little "tray" for the batteries.
You'll see it'll slide out and expose the batteries so you can replace them.
By the way, it takes two size 2032 lithium 3v batteries.