When you have multiple sources and want 5.1 you need a reciever. You might jury rig it with optical from the cable or Xbox but that's going to be for your installer to sort out.
Try 1800SAMSUNG to see if they will walk you through the connection and setup.
I have a samsung ku6300 4k tv
Xbox one s
Samsung ht-j5500 soundbar (with only 1 hdmi out port and no hdmi in)
And my comcast cable box.
How do i go about setting up the 5.1?
What audio settings do i need to set on the xbox, tv and receiver?