First and most important will be your brake light. Assuming you meant the brake light on the dash(warning light) check ur brake fluid level. As for battery have alternator tested.
Well first find out why they are on. The brake light indicates the the handbrake is stuck on where as the battery indicates a charging or battery problem.
You need to first take it to an authorized repair shop and have the brakes checked. If they are worn then have them replaced. Then replace you battery.