How and where do I change spark plugs on a 2001 Cadillac Deville?

My car was shaking after driving for awhile and someone told me that I had some cheap spark plugs in there. When I decided to change the spark plugs myself for the 1st time, I couldnt locate them. Can someone point me in the right direction? ThanksHow and where do I change spark plugs on a 2001 Cadillac Deville?you dont even know whats wrong...some guy told you? take it to a mechanic.