1. It is an audio adapter and recognized as a USB sound card / USB speaker when plugged in. No Bluetooth icon will appear on PC.
2. The pairing / connection via Bluetooth is between the C81 and your Bluetooth headphones / speaker, not the PC.
Step 1: Plug the C81 In your computer/PS4 /PS5.
Step 2: Get the C81 into Pairing Mode.
1st-Time Use: It'll automatically enter pairing mode. The LED indicator will rapidly Flash BLUE and White alternatively
Note 1.2: Non-1st Time Use: Press & Hold the MFB button on C81 until the LED indicator starts flashing BLUE and White alternatively
Step 3: Put your Headphones/Speakers into Bluetooth Pairing Mode.
Headphone / Speaker 1st-Time Use: The Headphone/Speaker should enter pairing mode automatically when powered on.
Note 1.3: Non-1st-Time Use: Merely powering on WILL NOT get it into pairing mode, you'll need to do so manually. Please either refer to the brand list below or refer to your Headphone/Speaker's user manual. You also can search on Google. E.g. “Bose QC35 Bluetooth Pairing Mode”
Sony, Bose, Jabra, Apple, Beats, Google, Sennheiser, Amazon Echo, JBL, Philips, Panasonic, Audio Technica, Bang Olufsen, Skullcandy, Bowers & Wilkins
Note 1.4: It is important to turn your cellphone, PC or any other previously paired-with devices' Bluetooth function off to avoid interference.
With both devices in pairing mode, give them a few seconds. Once connected, the indicator on C81 will turn Solid Blue (in music mode)