To turn off the light, you need to inflate your tires to the correct pressure. This pressure is listed:
* On a sticker inside the driver's side doorjamb. This is the most reliable source.
* In your owner's manual.
Once you've inflated all tires to the proper pressure, drive the car for a short distance (a mile or two). The light should turn off automatically after the system senses the correct pressure. If it doesn't, there might be a fault in the system, a persistent slow leak, or a more serious problem requiring attention from a mechanic.