Very confused

Hi all,
Currently using the Deadline theme by Awesem: https://demo.awesem.com/?theme=deadline

Heres my site: https://www.boxingasylum.com/main/

This is kinda hard to explain, but when you click one of the article links on the demo you see this: https://oi46.tinypic.com/2hevq8l.jpg

When you click one of the article links on my site you see this: https://oi50.tinypic.com/2vbafmf.jpg

On the main menu I have a sidebar, yet when I click an article the sidebar vanishes, but I’m left with the grey blank area of nothing and it looks terrible. How can I add stuff to fill up the space like they have in the demo?

Thank you. I hope you understand what I’m trying to say.