RCA RT2781H how to set up HDMI from tv?

Hi! I recently picked up an RCA RT2781H at Goodwill, and it has been awesome!

I currently have it set up with analog aux out to my tv, but I've been having issues with the sound system cutting out when the audio levels of whatever I'm playing get low, so I've been trying to switch to an HDMI set up.

My tv supports eARC, so I've been trying to get that to work, but I have not so far been successful. I'm new to this kind of thing, so I have tried to search the Internet for advice, and I have been looking at the manual, but to no avail. I found a portion of the manual that talks about setting up a tv on the system, but it talks about a tv mode source option that does not exist in the options for my system.

I would be grateful for any advice on how to get the HDMI set up properly, or also just how to fix the cutting out issue (I've tried some tv settings to try and fix that but once again with no success)

Thanks!