Knowledgebase
How to create Joomla categories and subcategories
You can create categories and subcategories from your backend's Category Manager. Either click on the Category Manager button on the backend's home page (control panel) or go to Content>Category Manager.
To create a new category click on the New button in the upper right corner of the Category Manager. On the Add A New Articles Category page that opens type a name for the category in the Title field.
If you want to, you can configure some of the other options. If you want the category to be a separate parent category, leave the Parent drop-down menu to the default No parent value. If you want it to be a subcategory, choose its parent category from the same drop-down menu.
In the text editor you can also type some information presenting the content or the general subject of the articles contained in the category. After all, the primary function of the category is to group articles on a similar subject. Don't forget to save the category after you're done configuring the options.
Visit the tutorial on creating Joomla categories and subcategories for some more information and screenshots.