We can help them significantly by pointing them in the right direction, showing them what we want, and providing them with the opportunity to do what we ask and figure out what we're talking about, but the no matter how many times you show a child someone else using a toilet, he won't fully understand what it's about until he experiences it himself. Essentially I'm saying that for a child to learn to use a toilet he has to experience using a toilet. It's really not. Since toddlers don't really care where they go, just like an untrained child can have an accident in his pants, so can he have an accident into a potty. All he needs is the opportunity.
Opportunity is the key.
But just as important, keep it pressure free. Children love to please their parents. They love to do new things and feel a sense of accomplishment for their successes. If we demand things of them that they're not capable of or not ready for, it should come as no surprise that they don't cooperate. He should be ready to sit on a potty or toilet.