In this video, the teacher explains the process of writing a thesis statement for a research paper. The steps include researching a topic, generating a big research question, restating the question as a complete sentence, and asking oneself if they are teaching something new. By following these steps, the teacher demonstrates how to create a thesis statement for a research paper on the topic of how mistakes caused some battles of the Civil War to begin. The importance of having a clear thesis statement is emphasized, as it helps the reader understand the overall purpose and message of the research paper.