If you are just looking for a starting point, you can enter your CV, the JD and anything else that might help (it can accept 000's of pages as input), then prompt it as specifically as possible, with something like "as a [current position] with [x] years experience in the [current sector], write a cover letter for [new position] at [new company]" then refine it's responses with further prompts.
"That was good, but talk more about my experience doing [something important]"
"That was good, but write it in the style of Donald Trump"
etc
If you are just looking for a starting point, you can enter your CV, the JD and anything else that might help (it can accept 000's of pages as input), then prompt it as specifically as possible, with something like "as a [current position] with [x] years experience in the [current sector], write a cover letter for [new position] at [new company]" then refine it's responses with further prompts.
"That was good, but talk more about my experience doing [something important]"
"That was good, but write it in the style of Donald Trump"
etc