First you can start out using the standard "five paragraph essay". It's what kids are always taught in school when they're stuck. It's practically the basis for any kind of essay.
So like the name states, there are five paragraphs in this essay. The first one would be your introduction. Your introduction should include a little background info on the topic of your essay as well as your thesis statement, which is just a sentence or two that essentially (but not literally) say "blah blah blah is what my essay's going to be about".
Second, third, and fourth paragraph will each be focused on three separate but strong/important points about your topic. In this, you will have deeper and more thorough information about the things that relate to these points.
The last paragraph is the conclusion. Depending on the person, this can be either the hardest or easiest thing to write in your essay. If you find this easy, then lucky you. If you find it hard like me, my best suggestion is to emphasize the strongest parts of your essay again but use different words. One of my English teachers said that a conclusion is basically summarizing what you just said in your essay with different words and smack a good feeling in the end. I can tell you that that is usually true.