At my new job, I am still learning how to do things. One of my co-workers, who is a nice enough person, does not seem to understand how much he knows about the job that I do not.
He said that he had told me everything about a weighing program we use. He actually had not. I have had to fill in the details so that I can use the program effectively.
I see this situation quite a bit.
Another example is games. You have a board game that you like playing. How easily can you explain to someone else how to play it?
Some people can not explain very well at all. One can get very confused trying to learn from them.
Some are very good at it. I am in this category, because I have worked at it. One of the benefits of a background in systems analysis is that I am good with how systems work. By breaking things down into their component parts, one can make a complex system simpler to understand.
That person who does not get how something works when you know quite well how it works is probably not stupid. He could just be missing a few details that are obvious to you but not to him.
How about giving him those details?