In menu Port you can manually setup COM-port number for oscill, but usually this made automatically.

COMxx - serial port PC: standard or virtual

Standard -  DB9 connector on PC, for uart.oscill with COM-adapter.

virtual - from USB VCP driver, for USB connected  usb.oscill or uart.oscill.

USBx - used for usb.oscill or uart.oscill with USB driver.

Find port - connected oscill port search. (library SiInfo.dll).

Show ports - open Windows device manager.