If you have the Seatalk to USB converter, then you can plug this straight in to a Windows, LINUX or Mac computer and use a Telnet Terminal type program to send this command. If you have the Seatalk to NMEA0183 converter, you need to use a NMEA 0183 to USB Adapter.

On a Mac we use CoolTerm which is freeware by Roger Meier…

https://freeware.the-meiers.org/

You need to make sure that CoolTerm is set to send CR+LF as the Enter (EOL) characters, as this is always used in NMEA 0183 systems to indicate the end of the sentence has been reached.

Then copy the command: $PDGY,STalk,On

And paste it into CoolTerm or any Telnet Terminal Type program and the mode should change.