Documentation on the Wikimedia sites is both about the tools the editors use and information about how the movement works. It's important that this is available in editors' languages so that they can work better. Documentation about the tools and how the wikis function is hosted on MediaWiki.org. Documentation about the movement is hosted here on the wiki we call Meta.
You can sign up for notifications at Special:TranslatorSignup. Some requests are also sent out at the Wikimedia Translators mailing list. You can also find older untranslated technical documentation. To translate to your language, enter the language code for your language.
If you're not familiar with the Wikimedia terms, there's a glossary that can explain many of them. Help:Extension:Translate/Translation example is an introduction to the Translate extension with examples.
If you need help, you can ask for it here:
Supported Languages on Meta can help you find others who translate texts about the Wikimedia movement to your language.
Supported Languages on MediaWiki.org can help you find others who translate software documentation to your language.