Welcome to the forum, Kate, and congrats on the new TV!
With the RX-750, I don't think that there will be much benefit from using the digital audio output on the TV. That receiver doesn't do surround sound, so left/right audio is just fine. My suggestion is to just use the headphone output on the TV. You can get a 3.5mm-to-RCA cable like
this one (pictured below, and many people sell them), and connect that headphone jack to one of the audio inputs on the Yamaha (such as the "CD" input). I think that will be the cheapest and best way to do it.