Many authors anguish over what to write in a cover letter, but the layout and content are simple.
Try and imagine it from the editor's point of view. While you've lived with your idea and writing for a few years, your editor has (hopefully) never read a story quite like it before. So, use the cover letter as an opportunity to entice the editor to read your submission. Tell us what you work is about; who wrote it, and why.
Dear Editor,
“A Golden Tangleweed” is an Adventure Romance set in modern times.
I wrote it after watching the movie “Gravity” and imagining what it would be like if those events took place in the asylum where I work as a nurse.
Although the protagonists have overwhelming odds to overcome, love finally prevails, but not quite where we expect.
It’s a feel-good story and I hope I’ve made the characters sympathetic, despite their location.
Yours,
...