The material list shows the materials that the script will choose from, use the buttons beside to add shadr nodes in your scene to the list:
Add by list: it will open a new window with a list of shader nodes that you can choose to add to the main list.
Add by Name: It will open a new window for you to type in spicified shade nodes and append them to the main list. You can type in multiple shaders, but you need to use a "|" between different shader names.
Add Selected: add the shader nodes you selected to the main list.
Add All: automatically load all the shader nodes in your scene to the main list.
There is also some commands for quick selection and manipulation the list items in the popmenu of the material list (RMB).
Use seed: by default, the script doesn't use a seed for generating random numbers, which means each time you press the "Assign" button, you'll get a different result. By turning on this check box, you can use the "seed" parameter to ensure the script return a same result for each seed number.
Bias: controlling the bias of random number sequence. Changing this parameter can let you get different results, especially useful when the seed number is set.
Treat connective Faces as Entirety: you can select the polygon faces and run this script. In this case, some faces maybe consecutive, for instance the face loops. By default, this script will treat all the faces separatly and you can give each face a different material. By toggling this on, the faces which are connected will be treated as a cluster and receive the same material.
Well, I hope the script can make your life a little bit easier, so enjoy it~:)