There are two parts:
xx.txt for the engine stuff
hedgewars_xx.ts/qm for the frontend stuff
where xx stands for your desired 2 digit language code (e.g. en = English)

Copy the English files (en.txt and hedgewars_en.ts; ignore the qm file) and rename so they match your desired language (Dutch).

Use any text editor (I'd recommend Notepad++) to edit the files. You could as well grab Qt's Linguist so editing the ts file becomes easier. Only thing left then is "compiling" the ts file to a wm file using Qt's lrelease or Linguist. If you don't know how to do that, just provide us with the updated text files (ts and txt file) and we'll do the rest for you.

Where do I find the .ts file? I only see te .qm files.

RemusJones

http://code.google.com/p/hedgewars/source/browse/share/hedgewars/Data/Locale

I'm almost done with the .txt file.
I'm on almost the half of the .ts file.
I translated the stuff too which says "<translation type="unfinished">"
Is that ok?
Or not?
Please reply.

Yeah, that's related to the translation to mark it as unfinished in Linguist. Just ignore it (or even remove the whole type attribute).

Ok.
This was wat it was before (or something like that):

|translation=typestuff...||(something)|

I made it like this:

|translation|Put text in here.|(something)|

The |'s are <'s and >'s
What I understand is that that's ok. If so, just ignore this or say it's ok. If not, tell me. I could have misunderstood it.

RemusJones

Sounds like you're doing it right.