HDMI eARC, or Enhanced Audio Return Channel, sends audio from your TV to a receiver or processor through a special HDMI port. It works like an Optical cable but handles more advanced audio formats. 

To use it, you will need CEC controls in the Anthem menu's Preferences section. You will also need to ensure this feature is enabled on your TV (which may be labeled under a different name on your other devices depending on the brand). Some common examples of this would be:

Anynet+ (Samsung)

Aquos Link (Sharp)

BRAVIA Link and BRAVIA Sync (Sony)

HDMI-CEC (Hitachi)

CE-Link and Regza Link (Toshiba)

SimpLink (LG)

VIERA Link (Panasonic)

If you are unsure of where to find this on your TV, please refer to the associated user manual. Once activated and configured correctly, your TV sends audio back through the HDMI cable for any connected source or bult-in apps (for Smart TVs).