OK,
I have just been on Iberdrola.es,
click on english on top right of the page,
then customers,
then e billing (you cant miss it),
then registering,
then complete the information required, then user registration then you should get a password and user id and then you indicate you want e billing From what i remember the hardestthing is remembering your user name and password.
Good Luck
Oauk