I'm new and happy user of Duokan alternative firmware for Kindle (Kindle 4 Black edition, sometimes referred as Kindle 5).

I wanted to add some new dictionaries, mainly English-English (lexical) and also Czech-English. All guides I'd found were outdated or didn't worked for me, so here is short summary. This should be universal process for any other dictionary.

Download dictionaries

You need three files per one dictionary: .idx, .dict and .ifo.

To download dictionaries go in this horrible site (someone should take care of it) and click to appropriate links, where you can find lists of dictionaries. If you are looking just for dictionary "some language" <-> english, go to dictd-www.freedict.de. For lexical-type (English-English) go to dictd-www.dict.org.

I choosed WordNet dictionary as Englsh-English (lexical) and English-Czech.

Installing dictionary

Now download appropriate dictionary and extract it. On Linux you can use this command: tar -xjvf <dictionary>.tar.bz2. On windows use WinRar or 7-zip.

Go inside extracted directory and you will find 3 files there. You need choose the one which ends with .dz and again extract it. It's zip format, so use zip or again WinRar or similar tool.

Now we have our three files. We will copy them to your Duokan system. Connect your kindle and paste these three files inside DK_System/xKindle/res/dict/.

That's all. I hope it helped you. If you have any problems, feel free to ask.

Caution

I found bug in Duokan 2014 (17. July) firmware on non-touch models of Kindle. You can't switch between dictionaries since you'd need touch the screen for it. Let me know If I'm wrong.