Which permisions needed to change language?

Hi All

I am kinda stuck here I installed spanish language on my 6.12 vrsion  but cannot seem to get the site to show in spanish  .. could it be a permission issue???

Any suggestions guys ?? I installe the language ...and the language key and strings for Spanish installed correctly ...but now flags show up on my site  so members could switch between languages ......any Idea of what file does this so i can chect to ensure it has the correct permission ??