The battery

I just baught prome suspects it is the last mystery case files I needed but I see the battery underneith the list on the right side what is it for and Big Fish needs to get Mystery Case Files- Millon Heir

In some scenes you will need to use your flashlight. To do that, you will have to have found a little battery in a previous scene on that round. The picture of a battery below your list shows that you have found it.