How do you turn on the antitheft system for a 2000 Chevy Impala?

The 2000 Chevy Impala doesn't have a separate "on" switch for its anti-theft system. The anti-theft system, likely the Passlock system, is automatically activated when you lock the car with the key fob or the key in the door.

There's no button to press to turn it on or off. It's always active once the car is locked. The system works by preventing the engine from starting unless the correct ignition key (with the corresponding transponder chip) is used.