How to program garage door opener?

A friend doesn't have owners manual and didn't even realize that her Blazer had a transmitter. She was trying to open cover to insert opener. There are 3 buttons and a red light. Oh, 1997 Chevy Blazer, how do I program the garage door opener?

Thanks....

Never mind this request. I found www.mygmlink.com and got my friend to register. It has online owners manual and with that, I quickly found the garage door opener programming instructions.