How do certain elite groups use force and propaganda to convince people to accept their orders and rules?
When elites can, they use propaganda that feeds on things that the people already believe. It is very difficult to make propaganda work if the people are not already disposed to believe it. The trick is to take beliefs that people already hold and figure out how to use them to support the goals of the elites. (For example, taking anti-American feelings in Iran and converting that into support for a nuclear program.)
It is only if this fails that elites typically use force. Force is a less efficient way to get a population to do what you want. It is much "cheaper" and more effective to use propaganda to make the people believe that your orders and rules are right than it is to force them to obey.