Do you feel as if there's missing documentation? As of now there's a few sections (detailed down below) to request documentation to be written.
General documentation has its own Github issues section and natives have their own section located here as well.
You can open a new issue by clicking on a green button that reads "New Issue", located on the top right once you access any of the pages detailed up above (Where are these sections?).
If you don't have a Github account, Github will prompt you to sign up for one.
For starters, your title should be descriptive, for example, if it's for missing docs, it should go something along the lines of "I'm requesting anyone to please document 'x' missing feature.".
If it's an issue within the documentation, you should indicate in the title that this is an issue within the documentation itself and for the description, you should indicate what exactly it is that is wrong within the documentation, preferably with a url/link pointing to it. A good example of such would be this, it tells the reader what the issue is, and points them to it.
There are several ways you can do this, the most common one is by creating a fork to the repositories (listed up above) and then creating pull requests from them. These will generally be reviewed by the community and elements, once approved they will be added to the documentation.
If you're not sure on how to fork a repository or create a pull request, you can check these out:
The other way you can help is by accessing PRs and correcting things that may be wrong or simply by contributing any findings you may have (upon research). Anyone with a Github account can contribute in any way.