You don't really configure the PIX, you just need to configure the sensor (via CSPM) to do blocking. When the sensor detects a signature that is set up for blocking, it will telnet/SSH to the PIX and add a "shun" command that will drop all packets from the signature source.
http://www.cisco.com/univercd/cc/td/doc/product/ismg/policy/ver23i/idsguide/ch03.htm#57747
Noe that for a PIX, there is no interface to apply this to, the shun get's applied to all incoming packets on all interfaces.
You then need to modify the particular signature so that one of it's Actions is to block.
http://www.cisco.com/univercd/cc/td/doc/product/ismg/policy/ver23i/idsguide/ch05.htm#xtocid263714
BTW, I would seriously consider upgrading your signatures, you are about 25 signatures releases and 4 service packs behind now.
