I don't know....I just clicked on the help button at the top to the right of hot deals, clicked on additional driver and copied and pasted to my post
It also says additional drivers can only be added at the check in counter. I don't know what I'm missing but all the info is on the Alamo website.
Mine says "at the counter or with Save Time." When I got my email confirmation, it had the option to prefill my info to use the kiosk- aka their Save Time feature. This is where you add the additional driver. There is nowhere to even put an Insider number for the additional driver.