To add / edit the documentation pages you need to send me an email address.
For now only translate the main page into Russian. You will see a 'translate' link above the page.
Don't mess with any of the API pages and hgy29 has a script that is updating that from the current help.
There is no problem if you want to add any more text/images to the missing documentation though.
The system uses some kind of markup language to show things like headings, etc https://www.mediawiki.org/wiki/Help:Formatting
In the docs internal links are normally added with double square brackets:
[[link to other page]]
But because we have translation you have to do it a slightly different way:
[[Special:MyLanguage/link to other page|<translate>link to other page</translate>]]
This will pass along the language you see from one page to another.
Once a page has been made and it has the translate tags on it then you will see a 'mark for translation' link.