http://aids.about.com/od/miscellaneousmeds/p/duragesic.htm
Look at this site for where/how to apply.
one tip when I used them in the past: I put them on my lower back as they pressure from sitting back on my pant waistline kept them in place. Oherwise, placing them on my arms or chest, etc, they always fell off, either from friction or sweat. Watch out not to expose them to heat - showers, hot tubs, etc.
As for pain releif, you should feel it within a day or so ... ask the pharmacist for the half life, etc as I forget. I know that I have a high tolernace to the drug and ended up needing more than one so keep your pain doc in the 'know' how well they are working.
Use fiber!
Good luck ... no one needs to be in pain ....