Translation is handled by Transifex. Simply register on the site and apply for membership to a translation team for your language. Approval may take some time.
Your Transifex email will be public in the created files.
For simple edits of the documentation just go to the page and click Show/Edit on Github on the left side, fork the repo, edit it, and submit a pull request.
For more complex additions I direct you to documentation for the projects we use:
We use Github Issues for our bug reports. Be sure to search on there for similar issues before posting your own, if it already exists pointing out you also have the issue never hurts. With the bug report include at minimum the information from help -> about.
Issues is not a forum for asking questions, please direct those to IRC for now.