Put the -ds.xml file into your JBOSS_HOME/server/YOUR_SERVER/deploy folder, and the .jar file, that contains the jdbc driver (for example postgresql-8.1-405.jdbc3.jar), put into your JBOSS_HOME/server/YOUR_SERVER/lib folder. Restart JBoss & enjoy (You must restart JBoss, while the lib folder is not hot deployable:))

You will find example configurations at JBOSS_HOME/docs/examples/jca folder (for example postgres-ds.xml).

More info at CreateAJDBCDataSource