Instructions on how to change the category of an article through the Joomla adminstrator back-end:
1. Log in to the Administrator back-end.
2. Locate Article by clicking on Content then Articles.
3. Click on the title of the article you wish to edit.
4. On the right of the page you will see the article's category. To change the article, click on the dropbown menu under the Category text. Select the most appropriate category. If there is no appropriate category, you can Save & Close out of the article to create your category and then return to edit the article.
5. Once you are satisfied with your updates, click on Save to save and continue to edit the article, or Save & Close to save the article and leave the article screen.