If you want to elaborate on a topic or fix a typo, there are buttons at the bottom of every article. You can edit a page with the built-in WYSIWYG editor, or plain Markdown editor on GitHub. This will submit your changes to the wiki's GitHub repository where the community would review and approve them. You can also submit a PR manually. In any case, you would need a GitHub account.
For further guidance, see the first page of the technical writer's guide.