in your module file, you will find the fucntion
 
	    public function getClientAddFields($package, $vars = null)
 
	add the fallowing code
 
        $user_name = $fields->label('Enter Username', 'username');
        $user_name->attach(
            $fields->fieldText(
                'username',
                $this->Html->ifSet($vars->username),
                ['id' => 'username']
            )
        );
        // Set the label as a field
        $fields->setField($user_name);
	for blesta password, you can't get the password, if you can got it, then you can send a exploit CVS to blesta