Key pad

If you mean the door code, the process is simple.

First you need the vehicles permanent five digit entry code. You can get that by having a Ford/Lincoln dealer scan the cars computer with a factory tool and retrieving the code.

You enter that code, within 5 seconds you then push the 1/2 button to enter the programming mode. (If you hold the button for two seconds all codes will be erased, the door locks will cycle confirming this) This essentially shuts down the ability to unlock the car using the keypad until a new code is programmed in.

Enter the new code you want. To add that to the personality system (one, two or three) push 1/2 button for position one, 3/4 button for position two, and five/six button for position three within seven seconds of entering the number code. The doors will lock and unlock to confirm code entry.
(If you do not understand that part - You can program all the setting like seats, mirrors, radio, heat and such. You can set those up so you get in, push a button and everything adjusts to your settings. You can add the key code on the door to that. Then when you use the keypad to unlock the door it will adjust all those items. You can set three different key codes for that system, so you could have one, spouse another and child a different one)

If you want to enter more codes for other personalities do it within seven seconds of the locks cycling after the last step.

At this point you can also program the remote key-less system if you do so within seven seconds.

To exit program mode press 7/8 and 9/0 together or wait until the door module times out.

Or the simpler process, have the same dealer that pulls the permanent code do this process. Just write down the code(s) you want to use and have them do the job. Should not take them long to do. Probably whatever they charge for a minimum.

I have always just pulled the number from the computer with the scan tool so I never really checked further. On all Lincolns the original number for the doors is in a sticker on the trunk hinge

(not after 2004)

Is the key a copy? If im not sure but I think those keys have a device in the key itself like a chip and if its a copy of the original key it would work everything except for the signal wouldnt be sent for fuel delivery.
If this is the case you can give the dealership the vin and they can get you a key