The instructions are in the owners manual in the glove box, and yes you do need two original keys or at least two progammed keys in order toprogram other keys.
1st) Put in one original key and turn key to the run position for 5 sec, and off again.
2nd) Within 10 seconds of removing the 1st key, put in 2nd key and turn to the run position and keep on for 5 seconds.
3rd) Remove key and within 10 seconds once again put in blank key and turn ignition to the run position and after 5 sec attempt to start vehicle. If it starts you now have a spare key. otherwise if it dont start you need to repeat those steps again.
To get a second key you will need to bring it to a dealership or call a locksmith, The locksmith is usually 20 or so dollars cheaper than the dealership and they can come to you for that. By then maybe you wont have to program the third key:)