Document Authentication in Germany

My family lives in Germany, but we are all US Citizens. We are adopting from China and need to have several documents (like police clearance) "Authenticated" by the Chinese embassy. What do we need to do in order to get these forms Authenticated? We are living in Kaiserslautern (so Rheinland-Pfalz). Also, can we get US-originating documents Authenticated or only German-issued documents? Thanks!!