The USB connection on the AIS is a serial/usb converter, and with the driver installed on the PC it should show up as a COM port in the Windows Device Manager, the same as using a converter/adapter or a USB
GPS. The driver is included in the ProAis2 software which is used to configure the unit, you can download that if you don't have it. If it was installed on the PC then the COM# should show up in Device Manager when the unit is plugged in. Setup that connection in OCPN.