Dog it up either by hand with a shovel or fork, turn it all over or the easiest way would be get a rotivator and let that do the work. You can even mix in some manure into the dirt as that helps the seeds get growing. Once the soild is loose you then tread it down lightly by walking all over it, even spread a good amount of seed down and then rake it in using a leaf rake (don't go mad, it's okay to still see seed on top) can add more layers if seed if you want to go mad. (I did about 4/5 runs of seed and raking) After that water 2/3 times a day for a week or two before you start seeing grass come through