How do you hardwire sirius radio to a 2004 silverado?

I'd start by purchasing a cigarette lighter hardwire adapter. This will allow you to plug in the cigarette adapter from the Sirius radio into the hardwire adapter. The hardwire adapter will have a positive wire that you'll add an inline fuse to. You'll also have a ground wire coming off of the adapter. With the positive wire, you should tap into an accessory wire at the ignition harness. You can make your own ground by using a self tapping screw and screwing into bare metal.