create dashboard menu for plugin

//create main menu 
function custom_menu(){
		add_menu_page(
			'firstPugin', //page title
			'First Plugin',  //menu title 
			'manage_options', //admin level 
			'first-pugin', //page slug
			'custom_admin_view', //callback function 
			'dashicons-dashboard', //icon url
			11, // menu position 
			 );
			 
			// create submneu
			
		add_submenu_page(
			'first-plugin', //parent slug
			'Add New', //page title
			'Add New',  //menu title
			'manage_options', //capability 
			'first-plugin', //menu slug 
			'add_new_function' //callback funtion   

		);
		add_submenu_page(
			'first-plugin', //parent slug
			'All Pages', //page title
			'All Pages',  //menu title
			'manage_options', //capability 
			'all-pages', //menu slug 
			'all_pages' //callback funtion   

		);
	}

	add_action('admin_menu', 'custom_menu');

	function custom_admin_view(){
		echo "This admin view of thi plugins";
	}