https://drivers.sfo3.digitaloceanspaces.com/Jamesdonkey%20A3R%20Driver.exe
The most up-to-date drivers can be found on JD's website: https://www.jamesdonkey.com/software.html (though the site in Chinese you should be able to easily pick the driver for your device as you'll spot A3 in the text)
NOTE: if you have a pre-existing install of the drivers you may need to uninstall it before installing the new ones.
Select English on the top.
FN+4 press for 4 Seconds and enter 2.4G Pairing mode, use this only if your receiver is not working.
FN+1 press for 6 Seconds to Enter Bluetooth Pair Mode.
FN+1, FN+2, FN+3 to switch stored Bluetooth devices.