Block Admin allows you to restrict access to the defualt WordPress admin panel.
You can install Block Admin directly from the WordPress admin panel.
Visit the Plugins > Add New and search for 'Block Admin'. Click to install. Once installed, activate and it is functional.
Manual Installation Block Admin plugin:
Download and unzip the file Upload the full extracted folder to the /wp-content/plugins/ directory Activate the plugin through the 'Plugins' menu in WordPress.
You're done! The Plugin ready to use according to the directions in the description.