So, you noticed your language of choice is missing a string or you just spotted a less-than-ideal translation and want to contribute the updated string, here is some hints for fixing the issue and properly submitting your modifications for inclusion in MantisBT.

For a start, prepare your workspace by downloading the latest source code

Remember to announce your work on mantisbt-lang@lists.sourceforge.net mailing list, so other translators will engage you if you are not the only contributor for the language

# register a user at http://translatewiki.net/wiki/Special:UserLogin?type=signup
# create a user page at http://translatewiki.net/wiki/User:YourUserName with a little information about yourself. Example: http://translatewiki.net/wiki/User:Horus
# request translator access at http://translatewiki.net/wiki/Project:Translator . This will take a few hours to be processed by a site administrator. Make certain you have created a user page.
* open strings_english.txt for reference
* open the file with your editor of choice; editor must support UTF encoding
* edit the strings and save the results
* run <code>svn diff > strings_<language>.patch</code> 
* open a new issue in http://www.mantisbt.org/bugs, attaching the patch file

Follow the same process as for updating an existing translation. Use http://translatewiki.net. Once your translated percentage goes over 40%, the language will be added to the MantisBT source code by the translatewiki.net staff