You need to push the button on your opener itself. Look on the back there should be a buton on the motor part that is grey and you need to push that then ge in the truck and push the button you want to use for the opener. Once it is trained it should open the door.
I ended up having to have a friend help me, he was inside the garage
I had the Ram parked just outside of the garage
he climbed the ladder & pushed the LEARN button
i was in the Ram, key on, remote garage door opener in hand & went through the process about 4 times until it finally worked
I had the same problem, I fought with it for awhile. Once I got it just a couple minutes and I was done. The trick I missed and I do not think is in the manual is first train it with your transmitter. The opener you are currently using. Put the transmitter it about 3" from your homelink and get it to learn from it. Push both the homelink and opener buttons at the same time. I think this gets Homelink on the right frequency.
Then I had to get homelink to be "accepted" by my physical opener. To do that I pushed the learn button on the physical garage door opener and then my home link button I wanted for that door. Bang it works, has worked great every since, has good range, more so than the small transmitters I have.
You need to clear the buttons on the truck first I think you need to hold down the two outside buttons till the the gauge cluster display say cleared book says 20 seconds but it could take up to over a minute. Now you set the home link with garage opener as others have described. That's what I needed to do to get mine to work.