Barannfin,
Brakes are applied (usually) by pushing on a brake pedal mounted at the top of each yaw pedal, with the toe of your foot, which often requires you to shift your feet up the pedal in order to get sufficient leverage.
Pedals are usually differential, giving the ability to use the brakes to assist turns whilst taxiing. Parking brakes are many and various, some requiring application of the toe brake, which is then 'locked' in place with the application of the parking brake, some have alternative parking brake independent of the toe brakes. Some helicopters have brakes for both pilot and co pilot, some are pilot only.
Most effective are those on skid helicopters, although they need a fair bit of power when taxiing......
