Model numbers would help since I don't know what connections are available on either of them.
If both the LG and TV have ARC (audio return channel) then you would connect the HDMI out of the soundbar to the HDMI (ARC) input on the TV. ARC has to be turned on in the TV menu.
If the TV and LG both have the same kind of output and input then use it. Optical audio out is the most common type on TVs so if your LG has that use a toslink cable to connect them. Other types are analog audio out (or headphone out) and coax digital out.
If they don't have the same type of connection then you will need an adapter like one of these http/www.parts-express.com/parts-express-dac-digital-to-analog-converter-%2851-compatible%29--180-999