List categories

I have the widget to list categories as links installed, it does just fine. It produces a list of categories as links, and when followed the link produces a page with all the posts in that category.

I would like to put the words “click on the article titles to read the full article…” because under the title is the excerpt, and someone new to bloggin might think that’s the article, and not click any of the title links to actually get to the articles.

What file do I edit to get that sentence to reside above the list of article titles?
thanks,
JSC