Well, what they mean by 'essay fashion' is an introduction, a few paragraphs that must link and flow well, and a conclusion.
I don't know the factors that influenced you, but I would start off in my introduction: 'There are a number of factors that influenced me in my decision to apply to St. Edward. I liked the prospectus, the campus was pretty, and it is a well-respected institution with an excellent academic record. Seeing as I am an aspiring law student, St. Edward would be the perfect opportunity for me to gain valuable skills needed for law.'
Then you would begin your first reason, elaborate on it, and link it back to the question. Every reason needs a new paragraph. Be concise.
Then, in your conclusion, reword what you stated in your introduction, perhaps adding a little more about your excitement at being part of the institution etc.
Make sure you read it through and make changes if need be.
Spell check and grammar check. So important.
Make sure it flows well - read it aloud or to a friend to judge this.
Anyway, I hope it goes well for you and I hope you get in!