It goes up to the air direction slide lever . Disconnect it there.
You release the other end ( inside your lower dash) when you've got that bent cover off. This is all from memory so stand to be corrected maybe.
When you're got the plate off take the opportunity to inspect the flaps for free movement and replace the sealing foam on the flaps too. Make sure that cable is in good nick and well oiled, any doubts replace it.