Back in CS5.5, InDesign added support for open-source Hunspell dictionaries to verify spelling and hyphenation.
In InDesign CS6, HunSpell is the default dictionary provider. Several dictionaries are shipped with the software, but you can also download additional spelling and hyphenation dictionaries from the OpenOffice website.
Using Hunspell to verify spelling and to hyphenate words, you are no longer limited by the number of languages shipped within the product. Dictionaries for over 90 languages are available for integration at the Open Office website. Several other sites also provide Hunspell dictionaries. You can download language dictionaries of your choice and add them to InDesign CS6.
To view the instructions, from within the product, click HunSpell Info in the dictionary preferences dialog box.
The instructions are also available at http://helpx.adobe.com/indesign/kb/add_cs_dictionaries.html