How to create simple 2-page site using 2 markdown files in github pages?

just create a file about.md with the content.
than you can link from your README.md to your about.md like so:
[YourLinkText For About](about.md)

I solved the issue.

The key is to include this at the top of the about markdown

---
title: Title
---

This helps github pages know the page is a markdown file that needs to be rendered.

The about page can be placed in the repo in an about.md file, and linked to from the main README.md file

One can create Multiple .MD Pages on GH-Pages

1. Create a new file about.md
2. At the top of this file, add the following:

---
title: ABOUT PAGE
layout: template
filename: about.md
--- 

3. Link this about.md in our Readme.md file using:

Go to [about page](about.md)

4. Commit your changes and push them to the gh-pages branch

Now, when you go to YOURGITHUBNAME.github.io/YOURPROJECTNAME/about.md, you should see the contents of your about.md formatted with the theme that you chose.