Lay out the two-stranded thermostat cable so that it goes to the humidistat from the humidifier and then connect it to the sail switch. Make sure you have enough slack in the cable to position each of the pieces accordingly.
Use the wire cutters to cut the cables to the length that it took to run the cable to each of the components in the last step, then use the wire strippers to remove about a 1/2 inch of the wire's rubber shielding.
Connect the conductors, which are white and black, to the humidifier's yellow wires. You can ignore the two red humidifier wires because they are not needed to make a proper connection.
Plug the two black conductors into the humidistat's terminals, then take the wire nut and fuse both of the white terminal conductors together.
Hook up the black and white conductors to the terminals on the sail switch labeled "Com" and "No." the "NC" terminal will not be used during the wiring process.