Cakephp3 custome form save in add with crud function

public function add() {
if($this->request->is(‘post’)){
$this->Crud->execute();
}else{
$characteristics = $this->loadModel(‘Characteristics’);
$character = $characteristics
->find()
->select([‘id’, ‘parent_id’, ‘name’])->contain([‘ChildCharact’])->where([‘Characteristics.parent_id’ => 0])->toArray();

    foreach ($character as $charact) {
        foreach ($charact['child_charact'] as $child) {
            $option_name[$charact['name']][] = array('id' => $child['id'], 'name' => $child['name']);
        }
    }
    $this->set(compact('option_name'));       
   }
}

Here form data not saved in db. I am using $this->set(compact(‘option_name’));
data in form input.I am using crud to using save data.