You have a brown (leaves) and a green (manure) so you have a start on a good compost pile. And certainly if you mix them together they will break down. Ideally to produce good compost, you would have more diversity of ingredients. We generally give a guideline of no more than 10% any one ingredient. Your pile would be 65% leaves and 35% manure (you generally want twice as much browns as greens).
I would also worry that a pile that is just leaves and manure would tend to pack down, not have any air channels. Are you intending to be turning your pile? Composting is an aerobic process.
You could improve it just by throwing in your kitchen scraps and yard waste including small twigs and sticks. The twigs won't break down as fast, but they help make air channels.