Resetting the Homelink garage door opener on a 2005 prius

My brother just sold me his 2005 Prius! (Yippee!) After reading the manual I tried to get the homelink garage door reprogrammed to my own garage door. I was able to get one (of the three) garage door openers to work but am unable to get the other two to take the code. Questions: Will only one code work for per door? I wanted to use the middle button for the garage door function but am only able to code the left. I checked the homelink website and found nothing that matched the information to the 2005 model. Also HOW do I reset them as they don't seem to respond as the first one did. Am I missing something here?