In order to add/delete a category in your blog, log in to the admin area and go to Posts > Categories.
To add a category, simply type its name in the Category Name field. If you wish, you can also type a category slug, description and choose a parent item. Then click Add Category and your new category will be created.
To delete an existing category, hover over it and then click the Delete button.
If you want to see a video tutorial on how to add/delete categories in WordPress, click Play Video on the screen below.
Find more useful WordPress videos at WordPress.tv.