How to add additional languages to my phpBB application?
To add more languages to your phpBB, download the desired language pack from this page.
The language pack file is an archive which should be first extracted. This will create a folder with the name of the language pack and inside it, you will see two more directories:
language
styleBoth of them should be uploaded in the folder of your phpBB. You can do that via the File Manager in Site Tools or via FTP.
Then install the new language pack. This can be done from your phpBB admin panel > Customize > Language Management > Language packs. If you have uploaded the files for the language pack correctly you will see it listed with an Install next to it, which you can use to perform the installation.