Run the PX-777 setup file or open CHIRP.

Plug the cable into the radio’s side port and turn the volume knob to about 50%.

Also, I'd like to mention that software and firmware for PX-777 may not be publicly available and users might need to contact the manufacturer or an authorized dealer to obtain it.

Turn off the radio, plug in the 2-pin connector firmly, and then turn the radio back on.

Always perform a "Read" first to sync the radio's current configuration to the software.

A Complete Guide to Puxing PX-777 Programming Software: Download and Setup