Click Content Pages in the administration menu. The next page will have a list of choices.
Select Articles and the following page will list all the existing articles on your site.
Click Edit next to the title of the article you wish to modify
Modify your Article's content
The next page will be similar to the page where you created the article. Here, you may modify any of the settings for the article. For further explanation of these settings, see Creating an Article. The main part of the article you will probably want to modify is the Content.
Save
Once saved, the article has been modified on the web site.