// ArticlesController
<?php
namespace App\Controller;

class ArticlesController extends AppController {

    public function create() {
        $article = $this->Articles->newEntity();

        if ($this->request->is('post')) {

            $article = $this->Articles->patchEntity($article, $this->request->data(), [
                'associated' => ['ArticleTypes']
            ]);

            dump($this->request->data);
            dump($article);

        }

        $this->set('article', $article);
        $this->set('articleTypes', $this->loadModel('ArticleTypes')->find('list')->toArray());
    }

}
?>

// ArticlesTable
<?php
namespace App\Model\Table;

use Cake\ORM\Table;
use Cake\Validation\Validator;
use Cake\ORM\TableRegistry;

class ArticlesTable extends Table {

    public function initialize(array $config) {
        parent::initialize($config);

        $this->addBehavior('Timestamp');
        $this->belongsTo('ArticleTypes', [
            'foreignKey' => 'article_type_id',
            'className' => 'ArticleTypes',
            'propertyName' => 'article_type'
        ]);

    }

}
?>

// create.ctp
<?= $this->Form->create($article) ?>
<?= $this->Form->input('title') ?>
<?= $this->Form->input('body', ['type' => 'textarea']) ?>
<?= $this->Form->input('article_type.id', ['type' => 'select', 'options' => $articleTypes]) ?>
<?= $this->Form->button('send') ?>
<?= $this->Form->end() ?>