You need to check if the FIFINE K050 is your input device:
Click on “System Preferences”, choose “Sound”, and go into the “Input” setting. Make sure to select the USB PnP Audio Device as the device for sound input.
Then, check if the FIFINE K050 is the input device in your recording software, like the QuickTime Player:
Open “New Audio Recording” and select the “USB PnP Audio Device” as the input device.
You can refer to the video below from 0:55 to 1:35.