Sound Bar

If you look on the left side behind the screen you will see the stereo analog jacks for making the connection directly to your TV. (You'll also find them on your receiver - usually at the back) Those jacks are red and white.  Depending on the stereo sound bar you buy, the cable may be included.

If you look at the manual - which you can find online here at HelpOwl - go to page 7 of the manual. You can enlarge the image for an easier read since it is a PDF. Just look for the + button.

There are also Virtual Surround sound bars which will usually include one or more type of connections: HMDI, optical and coax digital audio. They will also be more expensive.

A passive sound bar is a speaker and which you can connect to your receiver. Since you want to connect to your TV, just know that these are connected to your receiver just as if they were speakers. They will most often come packaged with speaker wire.

Do you want to amplify your bass?  Get a sub-woofer.

Not knowing what kind of system you have, I think you will need to do some shopping as there are different types of sound bars to meet your specific needs.

Which sound bar you buy depends upon your budget, your room size and what you expect it to do for you. Do you want soundtracks?  Do you have a home theater set up? Are you simply looking to improve the often weaker speaker system found on some Dynex models especially in a larger room?

The best sound bars cost up to $1,1100.  For that you could replace your TV.  Consider also that you can simply add speakers because even good quality surround sound bar with a sub-woofer can cost upwards of $250.00.

I suggest that you take a look online at several different stores who specialize in home electronics and read reviews. Start with the lowest ratings first.