There are numerous resources available for writing argumentative essays. Purdue University's OWL website offers a detailed discussion. The same website also offers this basic overview of the essay and its structure:
"A common method for writing an argumentative essay is the five-paragraph approach . . . If it sounds straightforward, that is because it is; in fact, the method consists of (a) an introductory paragraph (b) three evidentiary body paragraphs that may include discussion of opposing views and (c) a conclusion."
Depending upon the specific instructions of your assignment, including a discussion of opposing views, and rebutting those views, is crucial to writing a strong argumentative essay.
CSULB University Writing Center
"We offer a variety of tutoring services and workshops for students across the campus, from one-on-one in-depth consultations where you can get answers to your writing questions to workshops on . . . writing strong arguments, and proofreading for error-free writing."