Copy & paste the *.py file in to your Blender Install folder under addons.
%Path to Blender%\Blender\2.93\scripts\addons\*.py
Copy & paste the *.py file in to your Blender User folder under addons.
C:\Users\%User Name%\AppData\Roaming\Blender Foundation\Blender\2.93\scripts\addons\*.py
Just open Blender open "Edit"->"Preferences..."->"Add-ones"->"Install..." then navigate to the folder were you downloaded the script, select it and click on "Install Add-on".
How to use is:
When the Addon was installed and it can be found in the addon list under "Preferences..."->"Add-ones".
Switch to the "Shading" workspace or open a window of the node shader node editor.
Then just click and hold the "Y" key and it will open the Shader Type Pie Menu, select which you want to switch to.
How to change the shortcut:
Open "Edit"->"Preferences..."->"Keymap" make sure "Name" is selected and type "call menu" into the search field.
Look for the "Node Editor" category, and expand "Call Menu (PME)" make sure you can see "Shader Editor Pie Menu" in the "pie_menu_name:" field. by default, the shortcut is set to "Y" but you can adjust it to your liking.