Translators should start by downloading the tarball and translating the files to their language of choice. You can find more information about the process in the Translator's guide (of which this page is also a subsection of).
The translated files should be stored in contrib-cvs/translations/id where id is an RFC 4646 language code. If you don't know your code, ask on the translations mailing list.
You should only put the individual translated files in this directory. A script will generate a merged id.po file. Make sure to fill out the header section of each file and rename them from .pot to .po. Also make sure to start with the file general.po. This file contains strings that appear in more than one place and therefore will give you best results for least effort. It also is required to create the downloadable files. There is also an installer.pot file which will not get merged into the id.po file. This is used by the installer, and should not be imported to the Drupal database.
The translation of Drupal for Greek (Hellenic). Feel free to submit an issue for any corrections or suggestions.
The translation for Drupal 6 has been out there for a while now. You can download the latest version, but you are always welcome to submit suggestions or corrections through the issue queue.
The translation for Drupal 5 is complete.
The translation for Drupal 4.7 is complete, but not supported any more (Drupal 4.7.x and older versions have been deprecated, please upgrade to at least version 5.x, until the final version 7.0 is released).