Open ZDMC/KODI/XBMC and Hover over System and then click on Settings

Click Appearance

Hover over International and then click on Language

Choose the language of your country

When you do a clean install, or start ZDMC/KODI/XBMC for the first time you will have to set your default language, a language file could be installed from the internet at this time.

If you get gibberish as text, which can happen because of an unsupported language font, you need to go into your Skin settings and change your Fonts to a known font.

Change the font to Arial based, you could try others if the text is still gibberish.

Precautions