There should be documentation on your furnace that shows a schematic. Read through it and look for a section on accessory hookup. That will probably detail the location of 1/4" spade connectors on the controller board for both a humidifier as well as an electostatic air cleaner. You'll connect a hot and a neutral 110 volt line from the connectors up to a 24 volt transformer that powers the humidifier. Remember to shut the power off to the furnace first at the circuit breaker panel.