You’ll find this post in your posts directory. Go ahead and edit it and re-build the site to see your changes. You can rebuild the site in many different ways, but the most common way is to run hugo serve, which launches a web server and auto-regenerates your site when a file is updated.

To add new posts, simply run:

$ hugo new posts/my-sample-post.md

And you shall see the my-sample-post.md file in posts directory, just edit the front matter and content as you like. Take a look at the source for this post to get an idea about how it works.