College Persuasive essay?

Well it is my first semester in college and I am taking an english cl..I have never been very good at english and writing has always scared me. I have an a in this cl so far, but I am afraid I am going to bomb this persuasive/argumentative essay. I'm wring about the danger of keeping killer whales in captivity. I am very familiar with the topic and know how to argue it, but I am very afraid of citing and how to do it, as I have never written a research paper before. Any advise? My rough draft is due on wednesday and I am really afraid...if I forget to cite I know its plagiarism and that is scary,,has anyone written an essay like this? Is it nothing to be worried about?Thanks for help in advance.