Soil test kits are sold through the extension office. The county office is at:
430 Court Street
New Castle, PA 16101-3598
office hours: 8am-4pm
In the form that you send in with the sample you mark that you are looking either to establish the lawn or to improve the lawn. Recommendations will come back to you from the lab. About a cup of soil is needed, and there are instructions on how to collect the sample in the kit.