You can try
www.homelink.com and go to the FAQ section. once there you can email them and they will provide you with detailed instructions on how to program your Homelink transmitter. I have done it with my Sienna and it is not really hard as long as you dont have what is called a rolling code.
You pretty much jsut hold the button on the homelink transmitter you want to use for your garage door and hold the button on your garage door opener at the same time. When the light on the Homelink transmitter flashes rapidly it should be programmed.
I jsut found this online also. It is from the Mazda guide for programming but they are all the same. hopefully it will help you out. If you ahve more questions I would try the link I gave you above or doa search on homelink programming at Google.
http://www.mazdausa.com/MusaWeb/pdf/...ming_Guide.pdf
Linear Mode
