Customizing provides a nice interface for you to create custom post types, taxonomies and (meta) fields (meta boxes).
You’ll find the Customizing tools in the ‘Customizing’ menu.
In the ‘Custom Box’ screen, you may show and hide groups of fields, and order them the way you like.
All the settings are based on the WordPress API settings, therefore, the oficial guides apply to them.
Upload the plugin files to the
/wp-content/plugins/customizing directory, or install the plugin through the WordPress plugins screen directly.
Activate the plugin through the ‘Plugins’ screen in WordPress
Go to ‘Customizing -> Customizing Settings’ and check the tools you want to use.