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 Category dropdown menu to the right of the text areat. Select the most appropriate category. If there is no appropriate category, you can close the article, create your category, and then return to edit the article.
5. Once you are satisfied with your updates, click on Save to save your changes and continue editing the article, or Save & Close to save the article and close the article editing page.