You need to have the sirius receiver installed. It is a black box that sits in the rear of the car, and an antenna is installed on the trunk. The kit lists for $ 699. Dealer pays under $500, you can get it for $550 if you smile nicely. There are two versions, one for MOST, and another for D2B fiber optic cables. If you dont know which you have, just take your VIN into the parts department so you get the correct kit. You can install the hardware yourself, but you need to cut a hole in your trunk lid for some versions. There are other antennas that mount with sticky tape, or in the front grill in the hood. Disscuss these aternatives with the dealer folks. Some are willing to assist, others click their heels and just quote the party line of cutting the hole. After installation, the head unit needs to be "version coded" to know a satellite receiver is connected. The dealer connectes a laptop to the car and does some hocus pocus with the bits and bytes. The nav unit will display the ESN (electronic serial number) and the Sirius phone number to call to activate.
The purchase price of the kit includes a 14 month subscription, worth about $ 130.
I know there are $50 solutions to get Sirius in the car, but the integration with the speedo display, Nav display, and use of the wheel buttons are worth the price for me.