First thing, disconnect the negative battery cable. The '66 Fury uses a straight pull type switch. You will need to drop the trim panel from under the steering wheel. Then reach up and feel for a button tab on the switch. It is spring loaded and when you push the button, the shaft for the light switch can be pulled out of the switch. Once the nob and shaft is out of the way, there is a slotted collar that unscrews to free the switch from the dash. Once free, the switch can be lowered to disconnect the plug. Goes back together in reverse order. Suggest you locate a new switch so you can get a feel for how it works.
Dave