Get some organic material into the soil, but not much. It is easy to overdue that. But put all you can get on top of the soil and let nature take it down at it's own rate. In the interim you can jump start the process by using this product.
http://www.hortsorb.com/DIEHARD_BioRush.asp. A little goes a very long way. And I have no connection to this company, other than being a very satisfied customer.