Download and Install YAT using default options, then open it. If the Terminal Settings screen doesn't open automatically, select "Terminal" menu, then "Settings"

Select the COM port

If unsure of the COM port number, verify it with devmgmt.msc. Your Duet will be listed under Ports (COM & LPT) as USB Serial Device (COM#) or similar. Use COM# as the Serial Port in YAT

Set YAT to use <LF> as the end of line character. This will improve the readability of the messages coming from the Duet. Click "Text Settings" in the "Terminal Settings" and change "EOL sequence:" to <LF>. Click "OK" to close Text Settings. Click "OK" again to close Terminal Settings.

Select "Terminal" menu, then "Open/Start" to connect to your Duet. Or click the green tick in the tool bar. You may see lots of "WiFi reported error: no known networks found" messages. Don't worry, that's normal, and it means that the Duet is working!