Round out your introduction by providing your readers with a basic roadmap of what you will say in your essay to support your thesis statement. In most cases, this doesn't need to be more than a sentence.
If you've created an outline for your essay, this sentence is essentially the main subjects of each paragraph of the body of your essay. For example, if you're writing an essay about the unification of Italy, you might list 3 obstacles to unification. In the body of your essay, you would discuss details about how each of those obstacles was addressed or overcome. Instead of just listing all of your supporting points, sum them up by stating "how" or "why" your thesis is true. For example, instead of saying, "Phones should be banned from classrooms because they distract students, promote cheating, and make too much noise," you might say "Phones should be banned from classrooms because they act as an obstacle to learning."