Adding Author name to posts

Hi
I’m using the coraline theme for a single-author blog.
I would like to add the author name to each post (right next to “posted on…”), and am having a hard time figuring out how to do so. I’ve gone into the loop and tried changing a few things, but have had no luck, and I’m afraid to ruin something if i play around with it too much.
The blog is located at predictivestream.com

Any help on this would be appreciated!