Retract the blind to an upright and closed position as tight against the headrail as you can get it.
Grip the blind at both ends with your hands. Pull the bottom of the headrail out towards you to release the bottom from the bracket.
Slide the headrail towards you and down to remove the headrail from the top of the mounting bracket.
Remove the two screws that secure each of the plastic mounting brackets to the window frame or wall with a Phillips screwdriver.