Can't give you an exact answer without makes and model numbers of all your equipment.
No sure what you mean by double sound?
Does that mean that your DVD player is a home theater system with DVD built in? If you turn the volume of the HTS down then you won't get sound out of the soundbar and HTS at the same time.
In general you would connect the DVD HTS and cable box to the TV with HDMI. Connect the TV audio output (usually optical) to the soundbar. You may have to turn the optical output on, the TV speakers off and change the audio output type in the TV menu.
If the soundbar sounds better to you than the HTS you would only be using that as a disc player.