It is quite easy to add ckEditor to your custom form in Drupal. The only thing you have to do is, add the following lines to your form:
'#type' => 'text_format',
'#format' => 'full_html',
For example:
$html = 'some html';
$form['front'] = array(
'#type' => 'text_format',// to load the ckEditor options
'#format' => 'full_html',
'#title' => t('Front'),
'#value' => $html,
);
The above code will create a form element with its value inside ckEditor.