// config/bootstrap.php

Plugin::load('AdminLTE', ['bootstrap' => true, 'routes' => true]);

// src/Controller/AppController.php

public function beforeRender(Event $event)
{
    $this->viewBuilder()->setTheme('AdminLTE');

    // For CakePHP before 3.5
    $this->viewBuilder()->theme('AdminLTE');
}

// src/View/AppView.php

public function initialize()
{
    $this->loadHelper('Form', ['className' => 'AdminLTE.Form']);
}

// To customize configuration paste it at end of file config/bootstrap.php

Configure::write('Theme', [
    'title' => 'AdminLTE',
    'logo' => [
        'mini' => '<b>A</b>LT',
        'large' => '<b>Admin</b>LTE'
    ],
    'login' => [
        'show_remember' => true,
        'show_register' => true,
        'show_social' => true
    ],
    'folder' => ROOT,
    'skin' => 'blue' // default is 'blue'
]);