You need to know, that Real Category Management is able to create the category tree on the following pages:
- Posts > All Posts
- Pages > All Pages (Pro only)
- Products > All Products (Pro only, WooCommerce installed)
- Custom Post Type > All (Pro only)
After you have installed and activated the plugin successfully, and you should not see the tree immediately, you can activate it on the respective page under “Screen settings” in the upper right corner: Checkbox Tree View.