Not all routers have QoS options. The vast majority of routers that do have QoS are pretty much worthless. The concept of "priority" really only works on UPLOAD traffic and the vast majority of people need to fix problems with DOWNLOAD. The ISP is in full control over which data gets sent first and which get discarded. You need a very advanced form of QoS settings to even attempt to influence the download traffic and it technically is not really QoS it is attempting to trick end stations into requesting less traffic.