You should create a users model that extends Redbean's simple model like so:
class Model_users extends \RedBean_SimpleModel
{
private $_login = 'My default login name';
private $_password = 'My default not so secret password';
// The following method is executed right before an insert or update
function update()
{
$this->bean->login = $this->_login;
$this->bean->password = $this->_password;
}
}
Then you can simply use:
$user = R::dispense('users');
R::store($user);
Good luck!