I don’t use the fur shaders that often, but if you already had the “Furify” set it is fairly straightforward.
Use surface selection tool to select area of fur and then drag one of the shaders onto it (just use any one that has look close to it)
Then bring up the “Shader Mixer” tab and do “import from scene”, go to the “Image” brick and substitute the texture you want to use for the one that is already there.
Save this shader under a new name and also press “Apply” so updates will happen.
Any tweaks you can do in shader mixer or to a limited extent in surfaces tab.
Keep in mind that effect does not show until rendered