Just tell them why you are interested in their college and why you chose your field of interest. THAT's what they are looking for.
Also IDK if you have been working on MLA style in highschool or not, but make sure you have an introduction, three body paragraphs and a closing paragraph. Also make sure you have a thesis in the introduction. Yeah college is tough in some aspects, but I am sure you CAN DO IT!
Good luck to you in your college career!
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