sorry, missed that one.
it should be enough to add your translated file into the i18n directory, and you should be able to see it on the list.
else check with your configuration that you allow the specifiec language (or all) to be shown on the first page)
control panel -> configure -> system -> locale look in the bottom
If you have a problem, give us enough info of what you have done, what is configured in relation to your question.
Enable debugging and post it's censored but relevant info. Don't forget to write which version of SiT you're running.