If you have a Garage Door Opener that has rolling codes, you MUST follow the instructions in the Nissan manual to get the Nissan Homelink system to work. I don't know why anyone would tell you to discard that information because it's perfectly correct EXCEPT FOR ONE THING: The PHOTO in the manual.
Here's the problem: The PHOTO in the Nissan Manual shows the garage door remote control device being held next to the rear view mirror in order to enter the correct code. THIS WILL NOT WORK if you garage door opener is post 1993 and uses rolling codes. Depending on what garage door opener you use (Mine is a 2014 LIFTMASTER) you MUST use the special HOMELINK TRAINING REMOTE to program the Nissan Homelink codes into the vehicle. The HOMELINK TRAINING REMOTE comes with the Liftmaster opener. It has ONE LARGE WIDE BUTTON, not the three buttons that also come with the unit and will operate the opener without using the Homelink system.
If you try to use the 3-button remote that comes with the garage door opener (as illustrated in the Nissan manual) to enter the codes into the Nissan Homelink system, and if your opener is the more modern type that uses ROLLING CODES, you will find that the Nissan Homelink system will NOT accept the handheld remote code at all. The rapidly flashing light that shows when it DOES accept the code WILL NOT HAPPEN. Instead, use the single button HOMELINK REMOTE to enter the codes into the Nissan Homelink system. That's the only change to the instructions in the Nissan Manual.
You must then COMPLETE the rest of the process described in the NIssan Manual. So the sequence is this:
1) Clear all prior codes from the Nissan Homelink system as shown in the Nissan Manual
2) Use the HOMELINK TRAINING REMOTE (it has ONE LARGE button) to train the Nissan Homelink button holding the Homelink Training Remote next to the mirror while pressing the HOMELINK TRAINING REMOTE BUTTON at the same time you are pressing the desired NISSAN Homelink button (the button to be programmed); keeping them BOTH depressed continuously until the indicator flashes rapidly red on the Nissan Mirror. Then Lift your fingers from both buttons. Now you have entered rolling codes into your Nissan system, but you have not yet trained the garage opener to recognize those codes.
3) Put the Homelink Training remote aside; you don't need it for the rest of the operations. You now go to the Opener and depress the LEARNING button. It's usually a yellow button usually located where the wired switches connect to the garage opener unit. (lift up access doors if necessary on the opener but be sure the vehicle is parked outside so the door can operate without hitting your vehicle.)
You have 30 secs after you press the Learn button on the Garage Opener to get back into your Nissan and PRESS THE VERY SAME NISSAN Homelink button you recently programmed. Press and release it up to 3 times. Each time you press it, hold it for about 2-3 secs to give the opener time to receive the rolling codes. When it receives the proper code the door will operate. That's when you are done.
NOTE: If you have two vehicles with HOMELINK buttons that use the same opener (double wide door), you repeat these same steps in the other vehicle. You again use the HOMELINK TRAINING REMOTE (single button remote) to program the desired Homelink button in that vehicle. The method of programming each vehicle is very similar but some vehicles have a different indication that they have received the code (Lexus indicator goes solid GREEN for example). In all cases, once the Vehicle system has the code from the HOMELINK TRAINING REMOTE, you use only the HOMELINK button to teach the Garage Opener to recognize that vehicle's homelink buttton.
Of course the standard 2- or 3-button "clicker" that came with your garage opener ALSO will work with the opener. But that remote will NOT always work with the HOMELINK system. Best to use the HOMELINK TRAINING REMOTE. The reason is that, not only do rolling vs fixed codes affect the ability to properly program Homelink, but also modern Homelink systems operate at a different Radio Frequency than the older remotes. For this reason, if you garage opener is intended to work with a Homelink system, it will now usually come with a separate radio transceiver that is labeled as part of the Homelink system.