You can always click the Edit this page link at the top right of each page, but if you want to test your changes locally before submitting you can:
Fork the submariner-io/submariner-website on GitHub.
Check out your copy locally:
git clone ssh://[email protected]/<your-user>/submariner-website.git cd submariner-website make server
An instance of the website is now running locally on your machine and is accessible at http://localhost:1313.
Edit files in src. The browser should automatically reload so you can test your changes.
Eventually commit, push, and pull-request your changes. You can find a good guide about the GitHub workflow here.