The procedure to follow is:
Find and connect a USB to serial cable to the back of the switch, and the PC.
Find the COM port used by the USB cable. To do this, you will need to go into "Device Manager" and find the COM port number.
Start up the program PuTTY. You may have to download and install it. To download, search for "PuTTY" and download this link at the top this page:
Setup PuTTY with "Serial", the above COM port, and baudrate of: 19200
Then have them click on "Terminal" and select "Force on" for both "local echo" and "local line editing".
Then press "Open". To verify the connection send:
That should spit out the version. If not, verify the COM port and baudrate. Though if the COM port is wrong, PuTTY won't open a window.
Once connected you should send:
That will reset the switch to factory defaults and set the IP address back to DHCP, and clear anything else that might have been set during testing.
You may have to power cycle the switch to get it to connect using DHCP. At which point the switch will show up on the network.