laravel包命名空间不使用自定义命名空间

I'm using a simple package called Stolz to manage my assets .
each time i try to use the Stolz within my namespace it gives error
Main class

 <?php
    namespace Dashboard ;
    use View;
    use Stolz\Assets\ManagerServiceProvider ;
    class IndexController extends BaseController {

        public function Index()
        {
            $greeting = 'Welcome Here';
            return View::make('dashboard.index')->with('hello',$greeting);
        }
            public function Dashboard(){
                Assets::add('global/plugins/jquery.min.js');
                return View::make('dashboard.dashboard');
            }

    }

Error

Class 'Dashboard\Assets' not found