Add / Remove subscriber via PHP

Hi there. I would like to know how can I add / remove user to the subscribers list?
I looked at the examples here and made some function which I call after verifying data of the whole form. I tried to find some reference manual, to see which method is for what and which objects are for what, but without success.
One more thing – I will need one function for removing the user – but I have no idea how to do that since I don’t know which method is for what (and what methods are existing).

Here is my function:

function processMyWysija($idTmp){
	// $idTmp is id of WP user - it's successfully passed here.
	$idTmp = intval($idTmp);
	$userData = get_userdata($idTmp);

	$dataList=array('name','list_id');
	$modelList = &WYSIJA::get('list','model');
	$wysijaLists = $modelList->get($dataList);
	$arrlist = array();
	foreach($wysijaLists as $list){
		$arrlist[] = $list['list_id'];
	}

    $udata=array(
        'email'=>$userData->user_email,
        'firstname'=>$userData->first_name,
        'lastname'=>$userData->last_name,
		);

    $data=array(
      'user'=>$udata,
      'user_list'=>array('list_ids'=>$arrlist)
    );

    $userHelper=&WYSIJA::get('user','helper');
    print_r($userHelper); // here I expected some methods or something, only I got is WYSIJA_help_user Object ( ).
    $userHelper->addSubscriber($data);
}

Any help is appreciated. Thanks in advance!

http://ww.wp.xz.cn/extend/plugins/wysija-newsletters/