This is how you can translate Newsadmin to your language (in *nix).

1. xgettext ../admin.php ../archive.php ../functions.php -o messages.po
2. cp messages.po XX.po where XX is your language
3. Translate XX.po (I used kbabel for this, but a simple text editor will do)
4. msgfmt XX.po -o XX.mo
5. copy XX.mo to right place in ../locale (see finnish structure for an example).

Updating language

1. xgettext ../admin.php ../archive.php ../functions.php -o messages.po
2. msgmerge XX.po messages.po -o XX-new.po
3. Translate untranslated strings in XX-new.po and fix fuzzy strings (they are marked).
4. msgfmt XX-new.po 
5. copy generated messages.mo to right place in ../locale (see finnish structure for an example).
6. Restart (reload) webserver if new translations do not appear.