Well I’ve got bad news for you, training and helping people is part of my job, I teach them and help them do their daily tasks and the same people ask me the same questions over and over again.
You say “they need to know even if they’ll use it once or twice”? Well they will have forgotten when that happens because they don’t use it often enough to remember and computers aren’t something they’re interested in in the first place. The computer is their gateway to the internet, just like a car is someone’s way to get to work, the intricacies of how it works and how to do things that are unrelated to these tasks can be taught to them, they will not absorb the information.