By sticking your key in the door lock and turning.
Key
use key to manually unlock. manual unlock will not work.
A locked phone should indicate to you that it is locked when you push a button, or swipe the screen.
If you lift up the boot on the shifter, there's an override button which MIGHT work with a dead battery. Barring that, the best way is to connect a battery charger or another vehicle with jumper cables to it.
Replace the battery or jump the battery.
If the battery is dead the alarm will not go off
Use your key to unlock the door.
Use a slim Jim
Yeah... sorry but break open a window.
The hood should still open when the battery is dead
Call locksmith or local police dept.
With your key in the door lock cylinder.