The handbrake is located on the left-hand side of the driver's seat. It can be a manual or electric handbrake:
Manual:
Pull it up to activate it and press the button at the top to release it.
Electric:
To release, press the foot brake and pull the electric handbrake towards you. To activate, press the foot brake and push the electric lever inwards. When it is activated, a red light with a warning symbol lights up: