If you have a somewhat round remote, with 2 small buttons, sometimes blue and orange, sometimes both grey, this is how you program your remote
(To be 100% sure you're ready just disconnect your negative battery lead and fill your washer fluid while you wait 1min before reconnecting the battery. I also turned my headlights/fans off plus had my foot on the brake pedal the whole time I did this to make it as easy as possible.)
1. Get in vehicle and cycle key to the "ON" position 10 times withing 15 seconds, meaning pretty quickly. You will hear a beep or the horn will sound. (NOTE: Sometimes you have to turn it 11 times)
(I just rocked it between the ON position and the first back position that makes the dash lights turn off. I did it ton of times really fast until the horn honked.)
2. Open and close the drivers side door.
3. Press one of the buttons on the remote
4. Open and close the drivers side door.
5. **If you have other remotes, repeat steps 3 and 4 for all other remotes
6. Remove key from ignition, you should hear a beep/honk that the reprogramming has ended
7. Test remote(s)
I just thought I would add that this worked for my 03 Baja. It took about 2 minutes total to program 2 used Subaru orange/blue button remotes (from an 05 Baja) that I bought online. I was very happy with the info in this thread!