Update to 4 in STEP and README.md

.github/steps/-step.txt

@@ -1 +1 @@
-3
+4

README.md

@@ -14,25 +14,48 @@ _Create a site or blog from your GitHub repositories with GitHub Pages._
 </header>
 
 <!--
-  <<< Author notes: Step 3 >>>
+  <<< Author notes: Step 4 >>>
   Start this step by acknowledging the previous step.
   Define terms and link to docs.github.com.
-  Historic note: previous version checked the homepage content was not empty.
+  Historic note: previous version checked the file path. Previous version checked the front matter formatting.
 -->
 
-## Step 3: Customize your homepage
+## Step 4: Create a blog post
 
-_Nice work setting the theme! :sparkles:_
+_Your home page is looking great! :cowboy_hat_face:_
 
-You can customize your homepage by adding content to either an `index.md` file or the `README.md` file. GitHub Pages first looks for an `index.md` file. Your repository has an `index.md` file so we can update it to include your personalized content.
+GitHub Pages uses Jekyll. In Jekyll, we can create a blog by using specially named files and frontmatter. The files must be named `_posts/YYYY-MM-DD-title.md`. You must also include `title` and `date` in your frontmatter.
 
-### :keyboard: Activity: Create your homepage
+**What is _frontmatter_?**: The syntax Jekyll files use is called YAML frontmatter. It goes at the top of your file and looks something like this:
 
-1. Browse to the `index.md` file in the `my-pages` branch.
-1. In the upper right corner, open the file editor.
-1. Type the content you want on your homepage. You can use Markdown formatting on this page.
-1. (optional) You can also modify `title:` or just ignore it for now. We'll discuss it in the next step.
-1. Commit your changes to the `my-pages` branch.
+```yml
+---
+title: "Welcome to my blog"
+date: 2019-01-20
+---
+```
+
+For more information about configuring front matter, see the [Jekyll frontmatter documentation](https://jekyllrb.com/docs/frontmatter/).
+
+### :keyboard: Activity: Create a blog post
+
+1. Browse to the `my-pages` branch.
+1. Click the `Add file` dropdown menu and then on `Create new file`.
+1. Name the file `_posts/YYYY-MM-DD-title.md`.
+1. Replace the `YYYY-MM-DD` with today's date, and change the `title` of your first blog post if you'd like.
+   > If you do edit the title, make sure there are hyphens between your words.
+   > If your blog post date doesn't follow the correct date convention, you'll receive an error and your site won't build. For more information, see "[Page build failed: Invalid post date](https://docs.github.com/en/pages/setting-up-a-github-pages-site-with-jekyll/troubleshooting-jekyll-build-errors-for-github-pages-sites)".
+1. Type the following content at the top of your blog post:
+   ```yaml
+   ---
+   title: "YOUR-TITLE"
+   date: YYYY-MM-DD
+   ---
+   ```
+1. Replace `YOUR-TITLE` with the title for your blog post.
+1. Replace `YYYY-MM-DD` with today's date.
+1. Type a quick draft of your blog post. Remember, you can always edit it later.
+1. Commit your changes to your branch.
 1. Wait about 20 seconds then refresh this page (the one you're following instructions from). [GitHub Actions](https://docs.github.com/en/actions) will automatically update to the next step.
 
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