This is like super early so just take a few deep breaths first. I got in this May and I get it, I was in your shoes a couple months ago (oops, I didn't start the application until a week before, so don't fret), and I'll try to answer your questions as best as I can. You can write it whatever way you want, and even as a poem or a speech. All up to you. It can also be as formal as you want or not. I've read accepted applications of all types, I think they just want to see someone with something meaningful to say about themselves.