To write a new post, create a new markdown file in the _posts directory. The file should be named with the following format: YYYY-MM-DD-title-of-your-post.md. For example, if you want to write a post about customizing the favicon, you would create a file named _posts/2023-12-16-customize-the-favicon.md.
The file should start with a YAML front matter block, which contains metadata about the post, such as the title and layout. The rest of the file is written in markdown, which is a lightweight markup language that is easy to read and write. Markdown is often used to write documentation and is supported by many static site generators, including Jekyll.