What does it mean. tell them what you want to tell them tell them tell them what you told them.?

It refers to a teaching method for teaching students. It should read, "Tell them what you are going to tell them, tell them, tell them what you have just told them.

Tell them what you are going to tell them.;
Introduce the subject and the areas it covers, define what is going to be covered in the lesson.

Tell them;
Explain the subject matter in hand and its problems and solutions.

Tell them what you have just told them;
Consolidate what has been said, answer relevant questions and ensure the students have assimilated the information.