This tool can be found on the same folder where the Displax Connect is installed (Windows and macOS).
If you type "skin -h" you will see all the possible parameters you can use with the command "skin", the function of each one and how to use them.
Open a console (cmd.exe) and change the current directory to the same one where the Displax Connect was installed. By default it is: "C:\Program Files (x86)\DISPLAX\DISPLAX CONNECT\".
In Ubuntu the Displax Command Line tool is part of the environment variable of the Operating System.
That means you just need to open a Terminal and use directly the Displax Command Line tool.
Open a Terminal and change the current directory to the same one where the Displax Connect was installed: "/Applications/DisplaxConnect.app/Contents/Tools/Skin.app/Contents/MacOS/".