This is a step by step guide on how to replace and existing light with a new Double Switch. The process isn't complicated and taken step by step it can be done in a reasonable amount of time. br br FOR CEILING LIGHT EXHAUST FANS: br You will connect the blue and black wires from the light to the black wire to the switch, br br FYI: br 1. Always make sure the lines are NOT live while you are working on anything electrical. br 2. Make sure everything is up to code. br br My project was to install a ceiling light exhaust fan, then install a double switch so the vanity light can run off of one switch, and then have the ceiling light exhaust fan run on the other switch.