Sirius Satellite Radio E.S.N. code?

Hi I have a 2008 Ford Expedition with the Touch Screen Navigation and I want to purchase a subscription for Satellite radio and I need my 12 digit ESN code. When I got to the Satellite tab it says to call a number to activate is there anyway I can find my ESN code so i can activate online? Thank you!|||its the units serial number since its built in the number should be in your owners manual if not contact the dealer.