Basically what this is about is: Find the TV shows or Movies, download them from internet sources, store them locally (to your NAS) then watch them on any of the devices you might want to watch them from. (TV's, Rokus for those TV's that don't have client apps already, tablets, phones, computers, etc.) You can watch the shows locally (on your own network) or remotely (anywhere with an internet connection) on just about any device made.
The basis for this can be read right here: https://www.cuttingcords.com/home/ultim ... ng-started
This guy takes you through the basic set up, although it's on a Windows box instead of a NAS. One major advantage we have with the NAS is it can run 24/7, downloading everything as the system finds things, without you having to do any "extra" touching to make it all work. (I do a little bit of hands on, as I make sure everything is as Direct Playable as possible, from the start. You can read some of the details of that in my signature.)
This guy's setup uses Plex Media Server as the basis for sharing out the media. Plex Client apps are needed then, to play the media on the various devices. I will never, ever recommend anyone use uPnP or DLNA for streaming media or as a protocol set for watching it. Too insecure, and problematic as the amount of media increases.
All of the applications the link points to are available within the Asustor App Store. And unless you want some additional features from a Plex Pass, installing them are free. You will have to pay for your own internet connections, newsgroups subscriptions, etc. But other than that, it's all minimal costs.
I'm going to also recommend that, having gone to the trouble of setting all of this up, you take the time to also install PlexPy, which you can find here: https://forums.plex.tv/discussion/16959 ... program/p1. If you want to get really brave, you can go a step further and install Plex Request.net as well. All of the applications can be tied in to use PushBullet, as well as now, the logs from the NAS, so you can get real time notifications of new episodes, other users watching your media, etc.
the one thing this first link does that I don't like is he uses mkv videos. These are BAD joojoo on a small CPU NAS. So if you don't run some sort of conversion application or utility (like the one linked in my signature) you ARE going to experience buffering. The CPU on the NAS just can't handle transcoding, unless you have one of the beefier models. (700X runs great transcoding, and the 510x will work OK for up to 720p or so.)
And, for those of you that want to watch football or European football games, etc.. Plex can now be tied in with your HDHomeRun DVR system to record live streaming TV. I don't have the HDHomeRun myself, so I don't know the details, but I know it CAN be done. Don't ask me how...

I'll help anyone set the basics of this up, free on the forums or via PM's. If we need to take things to a TeamViewer session we can discuss rates.