If you have 2 existing keys programmed to your Focus, you can reprogram a new one yourself. If you only have one, you need a Ford dealer to do it. This is programming the key to the immobiliser, not remote door opening. A key which is not programmed will open the door manually, but won’t start the engine. Such keys are useful if you lock your keys in the car, or to give to your kids.
So if you have a Focus with 2 programmed keys, get a third, program it yourself and keep it safe; a cheap way to protect yourself against the expensive dealer programming costs.
I guess this applies to all Fords but I don’t know.