Cut it to wrap around the ignition switch tight, use a hose clamp and/or tape to hold it on and tight
Take some pam and spray it on the back of the ignition switch and the inside of the cardboard (alternately you could make slits in some plastic that match up with the terminal pattern and place it over the switch)
Put individual connectors on the wires
Put each wire on the correct terminal of the switch
Fill the cardboard tube with high temp silicone and allow to FULLY cure
Remove the card board
Remove the terminals and the silicon
Clean the pam off the parts / terminals etc with alcohol