Your page must be written in markdown, it should be put in the docs/ directory.
Please note that 'learn' (the documentation generator used) uses the first line of the file as the title. We usually put the title in h1, like this:
Title
=====
Section
-------
Text
After you wrote documentation, it's recommended to generate the website at least once, and check if it renders correctly:
$ ./learn.sh
$ # Then point your browser to ./www/
When you're done you can send a Pull Request.