Is the surround sound and "Theater System" only work while a DVD is played?

Hello,
I purchased this item in the store with the help of a store associate. I approached him and explained that I was retired law enforcement and very hard of hearing. I have had to become proficient with subtitles, however, while the use of subtitles has become the norm for me, it really bothers others who try to watch television with me, and subtitles get in the way of other information that may be displayed on the screen (name, organization, etc). But the problem is that I still have the old tube-type televisions. They still work great and I cannot afford the large flat-screen televisions. I asked my son to install/set up the system for me and everything seems to work fine with one exception: the speakers are only utilized while the DVD player is on and playing. Not exactly what I wanted. I would think "Home Theater System" should include the use of the surround sound while watching something on the television (cable programming). Is this correct or am I missing something? If it only works for the DVD player, I would think that the use of the term "Home Theater System" has been used entirely too narrowly here and would consider this a definitive case of false advertisement, not to mention the sales associate not knowing the products sold. So surely I'm not using this right, correct? Any and all help is surely appreciated!