How do I create a blogging page like this: http://mightymag.djwd.me/blogging/ ? / djwd Themes Support

Create a new Page and name it something like Blog.
From the dropdown menu at the right Page Attributes > Page Template select MightyMag Blog
Save the page
Now move to Settings > Reading
In Front page displays > Posts Page select the page you just created and click Save changes
Done! Now you can link the page in your main menu like in the live demo in Appearance > Menus