There are three basic points you need to consider to get an essay going.
First, you need a topic and thesis. This is the most important part of your essay. A good thesis is debatable. Perhaps the best way to explain this is to give an example. If you were going to write a paper on Oedipus Rex, a good thesis would be: Oedipus's downfall was due mainly to his pride. Not all will agree with this statement. So, it is debatable, which is what you want.
Second, if you will need reasons why you think your thesis is correct. The better your reasons are, the better your thesis will be. So, if we use the example above, then you are say the following about Oedipus. First, you can say that he thinks he can solve any problem. Second, you can say that he takes no advice from people (even the gods). Third, you can say that his pride ultimately blinds him.
Finally, you need a conclusion. Do not add new material here but summarize your thesis and supporting points. The goal is to bring resolution.