1. Open the hood of your BMW 330xi.
2. Look for a black or silver plastic cover on one side of the engine compartment.
3. If you see the cover, it likely houses the battery.
4. Remove the cover by lifting it up and pulling it towards you.
5. Inside, you will find the battery.
If you're still unable to locate the battery, consult your vehicle's owner's manual or contact a BMW service center for assistance.