populate checkbox value in text area
hook_node_presave($node) should be included in a custom module and not in your theme !

Look at Creating Drupal 7.x modules if you want to try so.

In your hook do something like that :

function norma_node_presave($node){ 

  $value = array();
  foreach( $node-&gt;field_checkbox['und'] as $checkbox){
    $value[] = $checkbox['value'];
  }

  $node-&gt;field_textfield['und'][0]['value'] = implode('&lt;br&gt;', $value);
}