I have translated all stings with PO-edit and managed

I have translated all stings with PO-edit and managed to create nb-NO.po and nb-NO.mo files and installed them in the language directory of the plugin ie.
wp-content/plugins/subscribe-by-email/languages

I then have edited wp-config.php to define('WPLANG', 'nb-NO');

I try to reload / restart my page, but cannot see any changes. The text is still english.

Two questions:
I do I do wrong or miss?
and
I want to contribute by offering my norwegian translation as a part of the plugin package for others that need it to use. Where do I send the files?

Regards Lars