DOES THIS COME PREWIRED?

Yes, each circuit has it's own wires coming from it already. You will have to tap into the side of your main panel, bring in the wires from the transfer switch and hook them up as per the directions provided. You can hook 1-2 together making either a 120switch or 240 which uses two switches. Again this is in the manual. It's quite simple for someone who knows how to do panel work. Recommend an electrician otherwise.

Yes, it is prewired. There are 6 red wires labeled A-F and 6 black wires labeled the same way. You would take the wire that is connected to the breaker in your home panel off the breaker, attach it to a black wire, then attach the corresponding red wire to the spot you just removed the wire from your home breaker panel. Do that 5 more times to the circuits in your house that you want to have power during an outage.