From the launcher, you can select your region and language at the lower left side by clicking Change Region, boxed in red in the screenshot below:
When you change your region, you will see the following pop-up to Select Language and Select Region as drop down selections.
Please find below a list of all Regions and supported languages:
EU Nordic and East
Please note: Changing your locale may result in the client needing to patch. The patcher will locate and downloading the necessary files for the selected region. These files include localized voice overs, text and some other effects. This process takes varying lengths of time, depending on the amount of localized content and the amount of patches that need to be downloaded.