The exact positioning may vary somewhat by model year, but the brake light switch in Toyota Corollas is usually in the immediate vicinity of the brake pedal. In many models, it is be mounted just above or just behind the brake pedal.
The brake light switch is mounted in such a way that it is in direct contact with the brake pedal. When the brake pedal is pressed, it engages the light switch. The brake light switch usually looks like a small button. The brake light should be off when the button is extended and turn on when the button is pushed in.