I watch TV from my laptop all of the time. I no longer pay for cable and stream everything I watch. It is extremely simple with an HDMI cable. Most laptops (not all desktops) have an HDMI port. If you have a Smart TV I’m sure it has an HDMI port. An older TV will probably not have an HDMI port. A regular HDMI cable runs from $12-15 on Amazon. Actually there are much cheaper ones but I’ve had good luck with the slightly better ones. Remember your picture can only be as good as your cable. One thing I’ve learned from experience is to get as short a cable as will comfortably reach. I’ve had more problems with my 25′ cable than with the 15′ foot cable. Also the cable can’t have anything pressing on it (furniture, etc.) as they are quite sensitive.
There is an adaptor to convert from USB to HDMI if you don’t have an HDMI port. A good one is about $60. Again, there are much cheaper ones but your picture depends on the quality of your converter.
I’ve watched two plays from Digital Theatre via HDMI from my laptop. They also offer the option of streaming from a tablet. You can keep the show in your library and stream it any time. I have another HDMI cable made to fit my Kindle Fire (one end is much smaller.) I stream Netflix and Amazon Prime from my Kindle to my TV and it works fine. Without having anything in my library today I couldn’t actually try it but it appears it will work with Digital Theatre. A Kindle Fire is MUCH cheaper than a laptop. You need a wireless set up for that to work but odds are if you have a Kindle you have wireless. It can also be used to stream from your android smart phone.
My big question for Digital Theatre is can you download it to your laptop or desktop to keep forever and still stream it if you log in to your account and go to your library? I remember DT saying you can download it three times (to three different devices I believe) but today I can’t find where it gives any limit. It seems like you can still stream it but I’d make sure I downloaded it before I streamed it. I have a Samsung Smart TV but it seemed much more difficult than using my cable so I gave up.
I got a little carried away with this but if I can help anyone please feel free to ask.