Usually with a Kindle based publication you stick to a fairly regular set of categories to work with.
Here I'll talk through pre-defining categories. It's also possible to create categories whilst editing a post, using the categories box, but it's generally better practice to prepare them in advance as you have more features to work with, including category descriptions.
You can visit, in the menu, Articles, then click on Categories.
At this point you are presented with a simple interface - on the right hand side the current categories, and on the left, you have a form for creating a new category.
The fields are:
Name for defining the category name or title.
Slug is the URL path to the category - this doesn't matter much if you're a Kindle publisher.
Parent if you have hierarchical categories you can use this, though we recommend you only use top level categories for the Kindle system.
Description helps you and, possibly, readers to understand the contents of the category. This isn't widely used but it's a useful exercise to complete.
You can edit a category after creation by hovering over it and clicking 'edit'.