Here are the basic process for editing a page and adding a new page. All steps start from your repository home page in GitHub.
Editing a page
Let’s make a simple change to the homepage (your index.md file).
Click on the index.md file.
Click on the edit icon (looks like a pencil)
Make some change to the text.
Hit the green Commit button near the bottom of the page.
Wait a few minutes and refresh your webpage.
Add a new page
Of course you’ll want to add your own pages. The GitHub website does not have an easy way to duplicate files. But we can do it manually.
Click on a file that is a similar kind of page to what you want to create.
Click on the Code icon for that page.
Copy the YML header to your clipboard, including the two sets of --- on the top and bottom
Click the Add file button
Type in the filename, including a .md extension
Paste your YML header on your new page
Hit the green Commit button near the bottom of the page
Edit the navigation bar
Now we need to add the new page to the navigation bar
Click on the _includes directory
Click on nav.html
Click on the edit icon (looks like a pencil)
Duplicate (via copy and paste) on of the lines that contains a link to a page on your site
Replace the old link with the name of the page you just created but WITHOUT the .md extension
Hit the green Commit button near the bottom of the page
Moving files
Go into edit mode for the file you want to move
Click on the filename at the top of the edit pane — this is called the file PATH
You can make this path into whatever you want / to create new folders.
If you in the edit textbox and you want to edit something that appears before the textbox, just put the curson on the far left of the textbox and hit backspace or delete and you’ll be able to edit it.