Yii2 theme integration

I have installed Yii2 advanced application, and now I want to change backend theme. How can I do this? Is there any file where I need to tell Yii2 that use my custom theme? I established my theme under backend/web/themes/mytheme. I just replaced this code in advanced/backend/config/main.php, but nothing happened!

 'view' => [
  'theme' => [
       'pathMap' => ['@app/views' => '@app/themes/mytheme'],
       'baseUrl' => '@web/themes/mytheme',
    ],
  ], 

Then I replaced this code under common/config/main.php but nothing changed!

Yet another approach to change theme in Yii2 is:

1. Create a themes directory in web folder in frontend or backend where you want to change theme.

2. place your theme folder inside themes directory.

3. change $css and $js variables in AppAsset.php in assets folder in frontend or backend like:

   public $css = [
       //'css/site.css',
       'themes/theme_folder/css/font-awesome.min.css',
       'themes/theme_folder/css/slicknav.css',
       'themes/theme_folder/css/style.css',
       'themes/theme_folder/css/responsive.css',
       'themes/theme_folder/css/animate.css',
       'themes/theme_folder/css/colors/red.css',
       //'themes/margo/asset/css/bootstrap.min.css',
   ];
   public $js = [
           'themes/theme_folder/js/jquery.migrate.js',
           'themes/theme_folder/js/modernizrr.js',
           'themes/theme_folder/js/jquery.fitvids.js',
           'themes/theme_folder/js/owl.carousel.min.js',
           'themes/theme_folder/js/nivo-lightbox.min.js',
           //'themes/theme_folder/js/jquery-2.1.4.min.js',
           //'themes/theme_folder/asset/js/bootstrap.min.js'
   ];
   

4. Do not include core bootstrap css, bootstrap js and jquery js as these are core APIs that are provided by Yii2. I have commented them above.

5. Use the below code to reference theme resources (css, js, images etc) in your main.php layout file or other site pages:

       <?= Yii::getAlias('@web/themes/theme_folder') ?>/images/margo.png
   

6. There is no need to include css or js files in layouts->main.php file :)

Create a view folder in your themes/mytheme and move all view files like main.php into it and other layouts needed.

Also you can set your basic layout in the backend\config\main.php like

return [
'id' => 'app-backend',
'layout'=>'yourtheme', //your `themes/mytheme/views/` contain yourtheme.php in this case
...

Also change pathmap to

 'pathMap' => ['@app/views' => '@app/themes/mytheme/views'],

In the backend folder make a theme folder .In file backend/config/main.php the components section add the code given below ,files in this folder will behave like the view folder in backend .

'view' => [
            'theme' => [
                'basePath' => '@backend/themes/demo',
                'baseUrl' => '@backend/themes/demo',
                'pathMap' => [
                    '@backend/views' => '@backend/themes/demo',
                ],
            ],
        ],