Having not applied for art myself yet took it at a-level i can understand the enthusiasm for it. I would suggest talking about artists that have inspired your work, how they have done that and how is it relevent to why you want to study the course. You could also say how being able to study this course will enable you to expand upon your experiences as an artist and hopefully will be able to fulfil your dream, a little corny but if this is your first draft then teachers should be able to help you out. Especially your art teacher(s). Don't know if this could help but it's a basic guideline towards what i did for my PS. =)