I uploaded an updated bitcoin.po for 0.3.1 attached to this message:
http://bitcointalk.org/index.php?topic=151.msg1259#msg1259
please use it if you're starting a new translation.
If you already have a po file, poedit can update it.
- Get the src directory from the 0.3.1 release candidate posted in the development forum, any version will do:
http://bitcointalk.org/index.php?topic=383.0
- Make a subdirectory under src: locale/??/LC_MESSAGES
(?? could be anything really, "en" or your language 2-letter code)
- Put your .po file there
- Open it with poedit
- In poedit, Catalog->Update from sources
The key is that the src directory with the sourcefiles needs to be 3 directories up from the .po file.