1. Login to the Control Panel at https://controlpanle.netfirms.com
2. Click Applications
3. Click WordPress
4. For the WordPress installation you wish to administer, click  the corresponding Admin link
5. Upon entering the WordPress Administration Panel, click "Manage"
6. Click "Categories"
7. For the category you wish to delete, click "Delete"

Note: Deleting a category does not delete posts from that category, it will just set them back to the default category Uncategorized.