Edit files using GitHub's text editor in your web browser (see the 'Edit' tab on the top right of the file)
Fill in the Commit message text box at the bottom of the page describing why
you made the changes. Press the Propose file change button next to it when done.
Then click Send a pull request.
Your changes are now queued for review under the project's Pull requests tab on GitHub!
For an introduction to the documentation format please see the reST primer.