Hello, I was wondering how I can activate the 'reading help' for Japanese in DeSmuME to comply to the 'Friendly Version'?^^

You can't turn it on. It is included in the rom, if you use the friendly version rom. There are two Japanese versions of the game. A normal version and a friendly version. The friendly version makes it possible for younger children to play the game, since furigana is added to the kanji, so that children can read it, even if they don't know the kanji.