Depends on what kind of sound bar you have. A digital audio cable should connect from the bar to the back of the television above the HDMI connections.
Depends on your sound bar options. Some have RCA style plugs (Red/White) others have .8MM plugs like headphones, others have optical plugs, and also there are HDMI options. I believe this TV has the option for RCA or optical audio and HDMI. Let me know which input your sound bar has and I'll see if I can help.
You can use the digital optical connection on the back of the tv.