To use the FIFINE K036 microphone with your smart TV + AV receiver for karaoke, you must:
Extract the audio from your TV in analog form (RCA or 3.5mm).
If your TV only has optical audio out, you’ll need a digital-to-analog (optical-to-RCA) converter.
Connect that analog audio to the K036’s audio input (R+L IN).
This allows the TV music signal to be sent to the K036, where it can be mixed with your microphone sound.
Output the combined mic + music from the K036 out (R+L OUT) to one of the analog input jacks on your receiver (like AUX/CD).
Select that analog input on your receiver, and you’ll hear both music and your mic through your home theater speakers.
More details are in our blog: Use FIFINE Karaoke Microphones System with Home Theater