How to Hide Material Design Admin Menus

function plt_hide_material_design_menus() {
	//Hide "Material".
	remove_menu_page('material-settings');
	//Hide "Material → Getting Started".
	remove_submenu_page('material-settings', 'material-settings');
	//Hide "Material → Settings".
	remove_submenu_page('material-settings', 'material-settings-page');
	//Hide "Material → Onboarding Wizard".
	remove_submenu_page('material-settings', 'material-onboarding-wizard');
}

add_action('admin_menu', 'plt_hide_material_design_menus', 11);

Where do I put this code?