To add a post to a category, you can do so using the Quick Edit feature in Posts. You can also do that directly from the Add or Edit Post page. When adding or editing a post, at the bottom right hand side of your screen, you’ll see a small box entitled Categories. You can simply check the various categories available that your article falls under. If however the category you want doesn’t exist, you can click on Add New Category to create the new category that you want for this post or article.
To manage all of your categories, hover over Posts and click on Categories. The Categories page will open up.
From this page, you’ll be able to do everything you need to with your post categories. On the left side of the screen, you’ll be able to create new categories. Simply enter the category name. The slug will be automatically generated for you, unless you would like to change it to something you prefer. If your category is a parent or top-level category, you can select None from the Parent option. If your category is a sub-category, then you can select the parent category from the options. For example, looking at the image below, you will notice that Local is a sub-category of News.
When you create sub-categories and you have them included in your navigation menu, this will produce a drop-down in order for your sub-categories to be visible. Below the Parent option is a text area where you can enter a description for your category. Once all is done, click on Add New Category to add the new category and make it available for organizing your posts.