heater air flow direction control

[gillyallen]

Hi, I hope somebody knows what I am talking about.
The knob you turn to change the direction of the air flow to the floor, body and windscreen is just freely turning not clicking or moving anything.
I bought my car second-hand and didn´t realise anything was wrong until the weather changed.
It is probibly cracked or shattered inside and what I want to know is how I take off the front fascia to get to the interior control so I can manual shift the position so the air flow is towards the windscreen on a permanent basis.
Any nice guys out there that can point me in the right direction.
I don't want to get out a sledgehammer to get to it, I'm sure it must be able to slide in one direction but don't want to start pushing and pulling until I know which that is.
Any help greatfully received.
Regards Gilly