How to install Italian laguages in an existing 11.5.10.2 existing instance

Hi,
We need to Install a new language (ITALIAN) on our instance DianaG1.
Please provide the installation instructions details and let us know if any syncronizazion with existing patches needs to be done.
The languages currently installed are:

CZECH                          CS   I
GERMAN                         D    I
SPANISH                        E    I
LATIN AMERICAN SPANISH         ESA  I
FRENCH                         F    I
DUTCH                          NL   I
THAI                           TH   I
AMERICAN                       US   B
VIETNAMESE                     VN   I

Regards.