ASA's uses QOS only in outbond direction.
It utilizes a single LLQ and matches
DSCP via class maps.
As far as configurations goes, you need to enable LLQ on an interface.Use class map to select traffic that you want to use in Queue and finally push traffic to the queue using policy map.
Following link will give you an example
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_tech_note09186a008084de0c.shtml
HTH
Syed Iftekhar Ahmed
