I agree a big pile is needed to adequately heat up. 3x3x3 like the one poster said is a good start I recommend bigger 4x4x4 but its what you have available and what amount you have available. Maybe in the fall you could get neighbors leaves they put out in bags on the side of the road for pickup, or find a horse stable who is giving away free horse manure. Usually they are more than welcome for someone to haul it off. The taller and larger the pile the better. Then of course adding the right mix of nitrogen and carbon your greens and browns. Check with your county landfill sometimes they have free mulch piles you can help yourself to where they chop up all the limbs and branches and grass clippings that will get you off to a good start usually.
As you build up your pile the microbes will start to work and as the exhale carbon dioxide the pile heats up in the center creating heat as things break down. Turning the pile get air and watering from time to time gets water in then turn it good to mix it up and the process starts over again.
Good luck and thanks Mike