how can I open my car?

Doesn't the alarm turn off when you turn the key in the ignition? Not a repair, I know, but will at least let you drive the car.
As Bryce says, you may need to replace the battery in the key fob, or it may need to be re-synchronised to the car.

phil 9
October 2009

open the back using a small screwdriver and check the battery size, replace the back quickly then go to any good supermarket or car spares shop and they should help to replace it and you will be able to turn the alarm off, or if you need to drive to a shop then open your car (make sure you have a 10mm spanner ready at hand) then if the alarm goes off you can open the bonnet, disconect and reconnect the battery, this will reset the alarm. it should take 2mins

Bryce
October 2009