Language pack installation (Multilingual User Interface - MUI)

SP 2013 allows multiple languages. Lets enable Arabic language in SharePoint.

Download and install Arabic language from Microsoft site. Download link
Double click & install setup file

After install--> Run SharePoint product configuration wizard to upgrade farm

Now we can check the installation from CA --> Upgrade & Migration --> Check product & patch installation status --> Here we can see the installed language pack

Now open any SP site --> Site Settings --> language settings --> select Arabic language --> ok

Open Browser --> Settings -->Advance Settings --> language settings --> select Arabic --> Add
Also move Arabic as a default language

Now refresh the site and it will display content in Arabic language.
It will not change the custom web part titles.

Reference: One,