Change size of featured image on site

Hi,

So I found where you change the size of the featured image but it changes it only in the archive section. When the post shows up on my site it shows up HUGE instead of being a thumbnail or smaller picture beside the initial text.

http://www.pawsoflife.org/blog

If you look at the blog now, the picture of the chickens with the logs or the picture of the dog sleeping under the bed is huge. How do I make it smaller?

Robin