You have to open the compartment. Look carefully on the bottom part of the remote. You have to press the small button to the left while simultaneously push it outward. It will take some time to do it, especially the first time. I did by using a penny to push the small button to the side and then pressed with my thumb to push the whole thing out. Once you get it a little out, use anything that is pointy and you should be able to pull the whole thing out. Be careful as you get it out, the battery will most certainly jump right out.

When you put the new battery, remember that the positive side has to face up towards you.

Hope this helps!