Thesis 1.8 How to make a specific thumbnail appear next to the excerpt

Hi,

I’m using Thesis 1.8 with Network News skin.

I want a specific photo to appear as a thumbnail next to the excerpt.

http://www.alpineathena.com/category/gear-reviews/

But the thumbnails keep using the first photo in the article.

Under the “thumbnail” section when I’m in the edit section of the article I place the correct link to the photo I want. And that photo is in my media files. But wordpress is still using the first photo in the article.

How do I change it to recognize the link to the saved in wordpress photo I want it to use?

Thanks!

Genevieve