Do you have Foxtel with Optus or are you using Fetch TV with the entertainment channels (I know theyr'e foxtel but it's through Fetch). If it's Fetch, then you can't. If it's actual Foxtel, then you'd need the right package.
Hi @Turner, further to what @SamSam has said, we do resell Foxtel on our Cable network in certain areas. If you are a Optus TV featuring Foxtel customer, you can call the team on 133937 to add the Sports pack to your service.
He's the channel information → http://www.optus.com.au/shop/entertainment/tv-movies/optus-tv-featuring-foxtel.
If you're a Fetch TV customer, Foxsports 506 is not available via Fetch TV