The humidfiers are extremely easy to set up.
Evidently there is one specific product where if you take of the outtake vent there are two holes into which aqarium tubing (5/8", I believe) fit perfectly.
From there it is easy to splice one of the lines into two so you have three tubes produced fog.
There are pictures of this in the kingsnake gallery, or at least there were. However, the last time I tried to find them nothing came up. Of course the search function was working poorly enough that I could not even find my own pictures.
Try the Boa constrictor specific forum as I believe on of the regulars over there has pictures up. Maybe type "Ultrasonic Humidifier Fogger" as your title and then ask some specific questions in your message.
I will offer two pieces of advice. First, have the humidifier as high or slightly higher than your highest cage. That way the mist won't have to travel "up" very far (only to the top of the tubing). Second, use RO or distilled water. This will greatly extend the life of your humidifier. Tap water or tap water run through a filter can ruin Ultrasonic humidifiers pretty quick.