indeed, was also unclear for me.
you have to configure the settings plugin to display these hmail plugins
/***********************
* settings navigation *
***********************/
// navigation config (requires plugin settings @website http://myroundcube/googlecode.com)
$GLOBALS['settingsnav']['moreuserinfo'] = array('part' => '', 'label' => 'userinfo', 'href' => './?_task=settings&_action=plugin.moreuserinfo&_framed=1', 'onclick' => '', 'descr' => 'moreuserinfo');
// navigation config (requires plugin settings @website http://myroundcube.googlecode.com)
$GLOBALS['settingsnav']['accounts'] = array('part' => '', 'label' => 'remoteaccounts', 'href' => './?_task=settings&_action=plugin.accounts&_framed=1', 'onclick' => '', 'descr' => 'accounts');
// navigation config (requires plugin settings @website http://myroundcube.googlecode.com)
$GLOBALS['settingsnav']['hmail_autoresponder'] = array('part' => '', 'label' => 'autoresponder', 'href' => './?_task=settings&_action=plugin.hmail_autoresponder&_framed=1', 'onclick' => '', 'descr' => 'hmail_autoresponder');
// navigation config (requires plugin settings @website http://myroundcube.googlecode.com)
$GLOBALS['settingsnav']['hmail_forwarding'] = array('part' => '', 'label' => 'forwarding', 'href' => './?_task=settings&_action=plugin.hmail_forwarding&_framed=1', 'onclick' => '', 'descr' => 'hmail_forwarding');
// navigation config (requires plugin settings @website http://myroundcube.googlecode.com)
$GLOBALS['settingsnav']['hmail_signature'] = array('part' => '', 'label' => 'signature', 'href' => './?_task=settings&_action=plugin.hmail_signature&_framed=1', 'onclick' => '', 'descr' => 'hmail_signature');
// navigation config (requires plugin settings @website http://myroundcube.googlecode.com)
$GLOBALS['settingsnav']['hmail_spamfilter'] = array('part' => '', 'label' => 'spamfilter', 'href' => './?_task=settings&_action=plugin.hmail_spamfilter&_framed=1', 'onclick' => '', 'descr' => 'hmail_spamfilter');
// navigation config (requires plugin settings @website http://myroundcube.googlecode.com)
$GLOBALS['settingsnav']['hmail_password'] = array('part' => '', 'label' => 'changepasswd', 'href' => './?_task=settings&_action=plugin.hmail_password&_framed=1', 'onclick' => '', 'descr' => 'hmail_password');
// navigation config (requires plugin settings @website http://myroundcube.googlecode.com)
$GLOBALS['settingsnav']['pwtools'] = array('part' => '', 'label' => 'pwreminder', 'href' => './?_task=settings&_action=plugin.pwtools&_framed=1', 'onclick' => '', 'descr' => 'pwtools');