You need power to open it, so you'll need another bettery and jump leads. Open the bonnet (US: hood) and look for the large connector marked with a "+" sign. Connect the positive lead to taht and the negative to the chassis (any clean connection). You can now use the normal opening method.
You can unlock the doors manually if you turn the key far enough. You can then open the hood and provide power to the vehicle with jumper cables and a donor car. If all else fails you can jack the vehicle up, support it on a jack-stand, and attach a red jumper cable to the starter positive red cable where it connects to the starter and then attach black cable to any metal place on the engine. You can use this procedure to charge the battery with either a battery charger for jumper cables from a donor vehicle.
in the trunk
think in trunk
in trunk, right side of rear panel.
Behind the right-side hatch in the trunk compartment.
One is in the trunk next to the battery and the other is in the glove box.
If it does not have a key lock you need to install a battery or jump from another vehicle to the batter connections.
Insert key and turn fully clockwise then push in knob and lift trunk
where is the battery situated on a 323i 1999 model BMW and hoe do i open the trunk if wont have power
under the back seat
under back seat
Remove the rear seat.
ask that @ a BMW shop i had the same prod with mine