The anti-torque pedals are located on the cabin floor by the pilot's feet and the pilot controls them with his feet.
The anti-torque pedals control only the tail rotor of the helicopter but not the main rotor. They are the only flight controls which control this rotor.
The anti-torque pedals are used by the pilot to:
When the pilot pushes the right pedal, the lift of the tail rotor is increased, yawing the helicopter to the right. When the pilot pushes the left pedal, the opposite occurs (for counter-clockwise-turning main rotors)
Pilot has to keep in mind that it is the cyclic control that changes the heading during a flight; the anti-torque pedals are used to compensate for the action of the cyclic control to maintain a coordinated flight