I found it: PHP: $this->getServer()->getInstance()->getPluginManager()->addPermission(Permission $perm); but how I will add permission if it isn't instance of Permission (Permission doesn't exists => variable-permission can't be instance of Permission).
He is asking how to register permissions, not to check permissions. If you just check the player has permission or not and you don't register permission, player cannot do the action after checking permission (It will return false)