1. Double-click the Computer icon on the desktop to open the Computer page, as shown in the following figure. 2. Then select the system properties, as shown in the figure below. Of course, you can also right-click "Computer" on the desktop and select "Properties". 4. On the system properties page that opens, select "Device Manager". 5. After the device manager pops up, you can see the item "Ports (COM and LPT)", as shown in the following figure. 6. Click the port option to display the current serial port list, which shows the information of all serial ports. If you don't know which one it is, you can plug in the serial port, and the one that responds is what you need. The serial port on the desktop defaults to COM 1.