Four ways to do it, from best to worst:
1. Go to any Directed Electronics (DEI) dealer and pick up DEI's 555F. It will bypass PATS during remote start, and you don't have to give up any of your keys. It comes with instructions. When programming the 555F to your car, you need TWO working Ford keys. www.directed.com
2. Buy any of the universal bypass modules out there. DEI 555U, Audiovox AS-TCBM, et cetera. You will need to permanently install one of your Ford keys into the universal module, and those keys usually aren't cheap.
3. You can make your own hand-made 555U with a relay and some scrap wire, but it can be hard for a novice installer to get this to work properly.
4. Pry the little plastic plug out of your key head; the PATS capsule will fall out. Glue the capsule to the ignition cylinder. (You'll have to experiment to find a spot that will work.) You'll also have to remove the capsules from all your spare keys, since the car won't start if it sees two capsules at once. This method is cheap and easy, but your car is unprotected against theft. And if that capsule comes unglued, the car won't start, not even with the key.