If both your LG and Samsung have ARC then you would need to turn it on in the TV audio menu. If either doesn't then you will need to add an audio connection from the TV audio out to an input on the LG HTS. Most common connection type would be toslink optical.
If both your LG and Samsung have ARC then you would need to turn it on in the TV audio menu. If either doesn't then you will need to add an audio connection from the TV audio out to an input on the LG HTS. Most common connection type would be toslink optical.