Before you lose all your sanity, ask LG if your model passes 5.1. My bet it doesn't.
In parting, here's how to connect and get 5.1. A little nutty at first to some but this generic formula works for most gear.
1. Source -> Receiver -> HDTV
2. For HDTV sound that is sourced from antenna, HDTV optical -> Receiver.
There are folk that scream that they don't want that setup but they usually figure it out after a lot of lost days.