Grab both keys, go inside the car.
1) Insert any key into the key hole and turn it to the 1 position (WITHOUT starting the car) and then turn it back to the zero position (as if you were turning the car off) within (I think) 5 seconds?. In reality this isn't difficult, just put the key in, turn it to 1, then to 0, then take the key off.
The next step must be done within 30 seconds.
2) Press and hold the UNLOCK BUTTON and then press the LOCK button (center button) three times. If done right you will see that the car will lock, and the unlock confirming the sequence. Put another way, you will need two hands. One will press and keep the unlock button pressed while the other one presses the lock button twice.
The important step is that you have to grab the OTHER key and do the same in step two within 30 seconds of programming the first key
This is so both keys get programmed with the same encryption... otherwise one key will end up having the new code but the other one won't.
So, to sum up:
Grab both keys; get in the car; start with one key; put it in; switch to 1, then 0; take key off; press and hold UNLOCK, and while holding unlock press LOCK three times; WAIT for confirmation of that key (car will lock, then unlock); upon confirmation; grab second key; and repeat to make sure both keys have the same code within 30 seconds.