Tih Blog Compact Documentation:
Categories
As we mentioned in Article’s chapter, every Article can be in some categories.
To add new Category form left menu, click on the link Categories -> Add New:

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In field Category Name fill with name of the new category. Press ‘Add’ to add
the new category*.
*If there’s already added category with that name, the new category won’t be added.
To view/edit categories form left menu, click on the link Categories -> View / Edit:

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To rename a category, click on the edit link, rename category and press update link.
To delete category, click on the delete link*.
*If there’s article on that category, the category cannot be delete.