Installing phpBB language packs
In phpBB, you can upload several language packs for your users to use. Every text string displayed by the system should be translated after you upload a new language pack. Using a different language pack does not change the contents of posts, as translating them is not possible due to the various content they can have and the limits of computer translation.
Language packs can be downloaded from the Downloads page on phpBB.com. To add a language pack, unzip the downloaded file and upload the contents to the
language/ directory. The files should be contained in a directory named with the language's ISO code, the default British English pack is in the
en/ directory for example.
To install the style imageset you should download the imageset for your language and unarchive the file/s into the relevant imageset directory (styles/prosilver/imageset or styles/subsilver2/imageset), again you must retain the directory structure. Once installed the imageset will become immediately available.
After you upload the files to the system, go to System->Language Packs. The pack should show in the Uninstalled language packs list. Click Install to add it to the board and make it available for users.
To make a language pack the default language of the board, go to General->Board Setting and set your language as default. Be careful though! Say that want want to change the default language after, let's say, 50 users have registered. These 50 users will continue to have the english language as their default. Only the new registered members will have the new language as their default. The same is true for time-zone. So, be sure, to set the correct timezone and language at first, when creating your forum.