We can't give you a precise answer without knowing the make and model number of the TV and soundbar.
ARC is audio return channel. If your TV has an HDMI input labeled ARC then you would connect an HDMI cable to that connection and to the HDMI connection on the soundbar. The TV menu will have a place to turn ARC on and set the audio output type. The soundbar will have a button to select the HDMI-ARC as the source.
If the TV doesn't have ARC then it will have a different audio output which hopefully matches an input on the soundbar. Most TVs don't have bluetooth so to use that with the soundbar is more involved.