Article Excerpts

I’m having trouble making it so that only the excerpts of articles show on the category pages of my blog. As it is, the entire articles show. My blog is at http://www.nccg.info. Any detailed help would be appreciated, as I’m not entirely expert at coding. I used the WordPress Theme Generator (http://www.yvoschaap.com/wpthemegen/) to make my theme.

-Derek