Welcome to CPF, uiko. For someone to be able to help we need more information. Do you want to use a brighter LED or does the one in the light not work? If it doesn't work, first try cleaning all the contact points. This is usually the cause of a non-working LED flashlight. Just get a cotton swab with some alcohol and go at it. Even a pencil eraser will take the corrosion off the electrical contacts. Good luck.
Geoff