I want to connect my 6-3 wire to a range box
Does the wire go in the lug only or in the lug and the copper slot also

Hi,
Generally your switch should have a twelve volt source. Often there will be a smaller wire connected to the same side of the solenoid as the battery. This serves to "energize" the wiring harness. A wire will connect to a smaller post of the solenoid that is the trigger. Without any numbers it is hard to say what and how many safety switches may be in the circuit and which pint they are used in the circuit.
Peace,
Clarke