Newbie - Automatic SPDIF (Optical/RCA)

I purchased the Automatic SPDIF (Optical/RCA) unit on a recommendation.
I want to have my WiiM Mini output to Automatic SPDIF then that to output to my speaker. Is that possible? Also there are 4 outputs - how does one select the right one to use? So far I’ve had no luck getting anything to pass through.

Commence laughter.