The spanish tutorial at http://my.opera.com/espanol/forums/topic.dml?id=90175 reads:
3º. Escribimos un nombre cualquiera y
una dirección de correo cualquiera (no
es obligado ni recomendable rellenar
los campos con datos reales).
Pinchamos en "Siguiente".
Translated here for you:
3°, Write any name and any email
address (not forced nor recommended to
use real data in these fields). Click
It seems that you should provide at least any data over here, and remember that the usernames on irc are at least 3 characters in length, and email addresses should be in email style format, like: email@example.com
Anyway, there are several ways to get into IRC channels, opera channels are majorly in Freenode, which can be reached by almost any IRC capable client, like Pidgin, xChat, irssi, etc.