As usual, without too much blah, here we go:

1. edit the configuration file (mine is /etc/oidentd.conf) as follows:

egg:~# cat /etc/oidentd.conf 
# Configuration for oidentd
# see oidentd.conf(5)
#
default {
        default {
                deny spoof
                deny spoof_all
                deny spoof_privport
                allow random
                allow random_numeric
                allow numeric
                deny hide
        }
}
[color=red]
user USER {
        default {
                allow spoof
                allow spoof_all
                allow random
                allow hide
       }
}
[/color]

NOTE: for each USER needed to be connected to IRC you add a stanza like in the example above (highlighted in red).

2. restart oidentd:

egg:~# /etc/init.d/oidentd restart
Restarting ident daemon: oidentd.
egg:~#