How to make Feature image visible


I am working on this site.
I have used this theme apparently(theme author) says, the theme is build in such way that when we add "Feature Image" via Wordpress Admin panel. It won't appear on the front end.

I want to enable it, could you please help me do this?
I want to achieve in all my following pages.
1. About Us
2. Forum
3. Petition.

Please let me know how can I do this.
I did add image here
But it is not visible.