Go to the releases tab. Scroll down to where you see assets. Click on the arrow until it is pointing down, then click on "setup.msi". It should start downloading the file.
Double click on "setup.msi" or click once if you are launching it from a browser. Go through setup as you normally would when installing programs. At the end, you can choose whether to open the README.txt file and/or open the program. I suggest reading the README.txt file for any additional information.
If you didn't choose to launch the program after start up, go to your desktop and double click on the shortcut. You have launched the configurator for the program, this is to change settings for the application. But for now, let's pair our bluetooth device with the application. If your AirPods or bluetooth device has not been paired with Windows before, go and pair them. In the configurator, click on the "Refresh/Scan" button. The program will start scanning for devices. After it is done, click on your AirPods or bluetooth device and click on "Apply Bluetooth Device". Now at the top, click on "Start Service". Now whenever your AirPods, or a bluetooth device connects to your computer, the pop up should pop up. If it is not working or these instructions confuse you, contact me.