Cover Letter Help!

Quicky background - when I was 17 I was young, and thought knew everything and was hired at the top LTC centre in my area in dietary. After being stalked by the manager who completely creeped me out and letting her boss know I was fired after working 6 days there.
Now I'm 25 and going to be graduating from my nursing program at the end of april. I spoke with the nurse manager on the palliative floor and she said she would hire me if HR approved me. HR said they want a resume and cover letter and in the cover letter saying I was let go from there previously and why I should be hired back.

How do I word this? I really want a job in this LTC!!!

Thanks