Installing Oracle WebLogic Server on Oracle Database Appliance - Update 11/2014
This is a pretty old discussion and there have been several releases on WebLogic on ODA since then. However documentation for the latest release (WLS ODA 12.1.3.0.0) is at Oracle Database Appliance Using Oracle WebLogic Server Documentation with step-by-step instructions at Installation and Configuration.
BTW the latest WLS ODA version usually appears on OTN first (before e-delivery) at http://www.oracle.com/technetwork/middleware/weblogic-oda/downloads/index.html