Code in controller:

    function action_submit()
    {
        if (Input::method() == 'POST') {
        // custom config for this upload
        $config = array(
        'path' => APPPATH.'tmp',
        'randomize' => true,
        'ext_whitelist' => array('jpg', 'jpeg', 'gif', 'png'),
        );

    // process the uploaded files in $_FILES
        Upload::process($config);

    // if valid files
        if (Upload::is_valid()) {
        // save them according to the config
        Upload::save();

        // let's check if we have something normally
        // here u wud call a model method to update
        // the db
        Debug::dump(Upload::get_files());
        } else {
        // process errors
        foreach (Upload::get_errors() as $file) {
        // file is an array with file info
        echo $file['message'];
        }
    }
    }
    }