Im playing movie from hdmi using WD device, i want to use my LG surround as output audio. Please help.

By WD device you mean a WD TV media box?
If your TV audio output is connected to your LG surround sound then you don't need to do anything,
If not then the WD box may have an optical and/or analog audio output.
If it doesn't then you can get an HDMI audio extractor