Random Texture is very easy to use. After you have installed the add-on, it will show up under the "Create" category in the "VIEW3D" display. The add-on have just three buttons:

Type: Decides if the add-on should create image texture node or principled BSDF nodes for your material. If you only want to randomise standard color images, "Image Texture" is the best option. However, if you want to randomise PBR textures, then choose "Principled BSDF".

Number of textures: Decides how many different textures you want to randomise.

Create Material: By pressing this button, you simply create the material (and node set-up) called "Random Texture". 

You can repeat this process for as many randomising materials as you like, their names will just follow Blender conventional naming i.e. "Random texture.001" etc.

Once you have created the material, just go to the shader where you can open the image textures you want or adding the different texture maps to your principled BSDFs depending on your preferred choice. A tip for PBR textures is by pressing ctrl+shift+T when "Node Wrangler" is enabled and when you have selected one of the principled BSDFs. Then you can load all the PBR maps at once. You can also adjust the node setup further however you like it.