WP Advanced Categories Widget
WP Advanced Categories Widget is a no fuss WordPress widget to display your categories with auto generated background image by taking the featured image from first post of each category. The widget is lightweight, simple to use and beautifully styled.
To install this plugin:
wp-advanced-categories-widget folder to the
Activate the plugin through the ‘Plugins’ menu in WordPress
Alternatively you can search for the plugin from your WordPress dashboard and install from there.
Visit WordPress.org for a comprehensive guide on in how to install WordPress plugins.