On a Blackberry Z10 it's just two touches: the first touch gets the main settings menu from the top (I think the same as any Android), then hitting the Hotspot icon. I use this all the time to feed the Internet to my laptop and even a couple pieces of remote machinery. I'd expect to do this to update such a car as well. And I'm really old in HN years.
How can carriers know when the phone is acting as a hotspot, and why are those bytes more expensive?