Well, the NAS has only DLNA/UPnP streaming server built in. So you should look in that direction.
PS The only thing that comes to mind - I am not sure if DLNA/UPnP is a routable protocol. Might be that it will only work on local LAN segment.
Otherwise it only knows how to serve files, that's it.
But that's OK, if you only need to connect to your share ovei Internet and double-click your movie file.