Hoi,
Typically you have set in your preferences the language you want to localise in. This will make the "translation tool" default to your language. Every language has a portal page for instance http://translatewiki.net/wiki/Portal:Hi for Hindi, there you find the "translation tool" as well. In addition there is the "language statistics" which is an alternate route into everything that needs localisation.

In addition people can give you the direct URL for something that needs doing .. http://translatewiki.net/w/i.php?title=Special:Translate&group=out-wikimediamobile&language=hi for instance is specifically for Wikimedia Mobile and Hindi. For some messages some background is provided in the "qqq" messages ..

We provide support in our IRC channel: irc://freenode/mediawiki-i18n and you can ask questions in our Support page :)
Thanks,
     GerardM

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